QB 63 
.B9 
1858 
Copy 1 



He telleththe number of the Stars, and calleth them all by their names." 



THE 



GEOGRAPHY OF THE HEAYENS, 



AND 



CLASS-BOOK OF ASTRONOMY: 

.ACCOMPANIED BY 

A CELESTIAL ATLAS. 
By ELIJAH H. BURRITT. A.M. 

GREATLY ENLARGED, REVISED AND ILLUSTRATED, 

BY H. MATTISOJST, A. M. 



NEW YORK: 
MASCOT BROTHERS, 108 & 110 DUAKE STREET. 

1858. 



QE>G2> 



Entered according to Act of Congress, in the year 1856. by 

P. J. HUNTINGTON, 

In the Clerk's Office of the District Court of the United States fo Mie Southern 

District of New York. 



Transfer 
engineers School UbQfe 
June 29,1331 



W. II. Tinson, Stereotypes C. A. Alvord, Printer. 



PREFACE. 



The rapid progress of the science of astronomy, for the last 
few years, has again rendered it necessary to revise the Geo- 
graphy of the Heavens — a work, the popularity of which is suffi- 
ciently proved by a sale of 250,000 copies. The editor has, 
therefore, availed himself of the occasion to make such improve- 
ments, both in the book and maps, as seemed to be demanded by 
the progress of the science, and the most approved methods of 
instruction. Among these improvements we may mention the 
following : — 

1. The matter of the book has been thoroughly assorted ; the 
most important paragraphs being printed in large type, and 
numbered, as in most modern text-books ; while that which 
seemed in the main explanatory of the more important portions, 
is left in small print. By this means an agreeable variety is 
afforded to the eye, while the book is made to contain far more 
matter, and is, consequently, far more complete, than it could 
otherwise have been. 

2. A new set of Questions has been prepared throughout. 
These are brief, topical and suggestive ; and numbered to 
answer to the paragraphs to which they relate. 

3. A complete list of Telescopic Objects in each constellation 
has been inserted ; giving the Right Ascension and Declination 
of each object ; with a brief description of it ; and easy land- 
marks and directions by which it may be found ; and references 
to telescopic views of the same in the new maps. The color and 
relative magnitude of the components of the double stars, are 
also given. These Telescopic Objects, compiled with great labor 
from Smyth's Cycle of Celestial Objects, will be found especially 



IV PREFACE. 

valuable to all institutions having an equatorial telescope. 
Indeed, they greatly enhance the value of the work for all 
classes of students. 

4. Several small constellations that were delineated on the 
maps, but were not described in former editions of the book, 
have been described, and their history given in the present 
edition. 

5. The page of the book has been greatly enlarged, for the 
double purpose of printing more matter and in larger type ; 
and to afford scope for wood-cut illustrations. Of these, great 
numbers have been introduced into the second part of the work, 
adapting it, in this respect also, to the wants of both teacher 
and student. 

6. Still further to illustrate the second part of the work, the 
first map of the atlas has been re-drawn and re-engraved, so as 
to illustrate more and better than the old map. 

1. Two entirely new map have been introduced into the Atlas, 
containing views of eighty different celestial objects ; such as 
Double Stars, Clusters, Nebulae, Comets, &c. These are 
all referred to in the book, and in turn refer from the objects 
back to the page of the book where they are described. These 
maps and the corresponding descriptions in the book will be 
found not only extremely interesting, but of incalculable value 
to the student. 

8. A chapter on the history, structure and use of Telescopes, 
Transit Instruments, &c, has been introduced — a subject which 
every student of astronomy should understand, but one to which 
no attention was given in the previous editions. 

Such are some of the principal new features of the present 
edition — larger type, new questions, telescopic objects, new maps, 
new matter, and numerous illustrations, making it the most per- 
fect and complete text-book of astronomy ever offered to the 
American public. 

H. Mattison 

New York, April, 1856. 



CONTENTS 



PART I. -THE CONSTELLATIONS. 



CHAPTER I. Constellations on the meridian in November, 



II. 

III. 

IV. 

V. 

VI. 

VII. 

VHI. 

IX. 

X. 

XI. 

XII. 



December, 

January, 

February, 

March, 

April, 

May, 

June, 

July, 

August, 

September, 

October, 



XIII. Variable and Double Stars — Clusters and Nebulas, 

XIV. Via Lactea, or Milky- Way, .... 
XV. Origin of the Constellations, .... 

XVI. Number, Distances, and Economy of the Stars, 
XVII. Falling, or Shooting Stars, .... 



PART II. -THE SOLAR SYSTEM 

CHAPTER I. General Phenomena of the Solar System, History, &c, . 

" n. The Sun — His Distance, Magnitude, &c, .... 

" ELL The Primary Planets — Mercury, Venus, &c, .... 
" IV. The Moon — Her Distance, Motions, Phases, &c, 

" V. Solar and Lunar Eclipses, 

" VI. Primary Planets continued — Mars and the Asteroids, 

" VII. Primary Planets — Jupiter and Saturn, 

" VHI. Primary Planets — Uranus and Neptune, 

" IX. Comets — Their Nature, Motions, Orbits, &c, .... 
" X. Of the Forces by which the Planets are retained in their Orbits, 

" XL Proper Motion of the Sun in Space, 

" XH. Precession of the Equinoxes — Obliquity of the Ecliptic, " . 

" XLU. Philosophy of the Tides, 

" XIV. The Seasons — Different Lengths of the Days and Nights, 

" XV. The Harvest Moon, and Horizontal Moon, .... 

" XVI. Refraction and Twilight, 

" XVn. Aurora Borealis and Parallax, 

"XVIII. Practical Astronomy — Reflection and Refraction of Light, 

" XIX. Refractors and Rejectors, 

" XX. Problems and Tables, ... 



PAGE 

18 



66 

73 
84 
100 
110 
122 
129 
135 
141 
143 
148 
154 



163 
171 
177 



245 
249 



270 
2S0 
287 
293 
297 



313 



INDEX TO THE CONSTELLATIONS. 



PAGE 

Andromeda 18 

Antinous 118 

Anser et Velpecula . . . .121 

Aries .... 28 

Argo Navis 62 

Aquila 118 

Aquarius 131 

Auriga 49 

Bootes 84 

Camelopardalus 51 

Oancer 64 

Oanes Venatici 83 

Canis Major 59 

Canis Minor 56 

Capricornus 127 

Cassiopeia 22 

Centaurus ...... 88 

Cepheus 25 

Cetus 32 

Columba 46 

Coma Berenices 77 

Corvus 78 

Corona Australis 118 

Corona Borealis 94 

Crater 71 

Cygnus 124 

Delphinus 122 

Draco 110 

Eridanus 47 

Equuleus . . . . . . 131 

Gemini 53 

Gloria Frederica 134 

Hercules 103 



PA«E 

Hydra 71 

Lacerta 134 

Leo 66 

Leo Minor 69 

Lupus (The Wolf) .... 90 

Lepus (The Hare) .... 45 

Libra 91 

Lynx 52. 

Lyra . . . . . . .112 

Monoceros 53 

Musca 32 

Nocta 88 

Ophiuchus 107 

Orion 41 

Pegasus 129 

Perseus 35 

Pisces 20 

Pisces Australis 133 

Sagittarius 116 

Sagitta 121 

Scutum Sobieski 116 

Scorpio 100 

Sceptrum Bran den burgium 49 

Serpentarius vel Ophiuchus . . 107 

Serpens .93 

Sextans 70 

Taurus 38 

Taurus Poniatowski . . . .115 

Telescopium Herschellii ... 53 

Triangulse 31 

Ursa Major 73 

Ursa Minor 96 

Virgo SO 



INTRODUCTION 



1. Astronomy is the science of the heavenly bodies — the Sun, 
Moon, Planets, Comets, and Fixed Stars. 

2. In entering upon this study, the phenomena of the hea- 
vens, as they appear on a clear evening, are the first objects that 
demand our attention. Our first step is to learn the names and 
positions of the heavenly bodies, so that we can identify, and 
distinguish them from each other. 

In this manner they were observed and studied ages before books were written, and it 
was only after many careful and repeated observations, that systems and theories of 
Astronomy were formed. To the visible heavens, then, the attention of the pupil should 
be first directed, for it is only when he shall have become, in some measure, familiar 
with them, that he will be able to locate his Astronomical knowledge, or fully compre- 
hend the terms of the science. 

3. For the%sake of convenient reference, the heavens were 
early divided into constellations, and particular names assigned 
to the constellations and to the stars which they contain. A 
constellation may be defined to be a cluster or group of stars 
embraced in the outline of some figure. These figures are, in 
many cases, creations of the imagination ; but in others, the 
stars are in reality so arranged as to form figures which have 
some resemblance to the objects whose names have been assigned 
to them. 

These divisions of the celestial sphere bear a striking analogy to the civil divisions of 
the globe. The constellations answer to states and kingdoms, the most brilliant clus- 
ters to towns and cities, and the number of stars in each, to their respective population. 
The pupil can trace the boundaries of any constellation, and name all its stars, one by 
one, as readily as he can trace the boundaries of a state, or name the towns and cities 
from a map of New England. In this sense, there may be truly said to be a Geography 
of the Heavens. 

4. The stars are considered as forming, with reference to 

1. What is Astronomy? 2. What first studied? First step? 3. How are the 
heavens divided, and why? What is a constellation? What of these figures? In what 
sense may there really be a " Geography of the heavens ?" 4. How are the stars 
classified, as respects their magnitudes? What expedient for designating their places 
in the heavens ? 



10 ASTRONOMY. 

their magnitudes, sixteen classes ; the brightest being called 
stars of the first magnitude, the next brightest, stars of the 
second magnitude, and so on to the sixth class, which consists 
of the smallest stars visible to the naked eye. The next ten 
classes are seen only through telescopes. 

In order to be able to designate with precision their situa- 
tions, imaginary circles have been considered as drawn in the 
heavens, most of which correspond to, and are in the same plane 
with, similar circles, supposed for similar purposes, to be drawn 
on the surface of the Earth. 

5. In order to facilitate the study of Astronomy, artificial 
representations of the heavens, similar to those of the surface of 
the Earth, have been made. Thus, a Celestial Atlas, composed 
of several maps, accompanies this work. Before, however, pro- 
ceeding to explain its use, it is necessary to make the pupil 
acquainted with the imaginary circles alluded to, called the Cir- 
cles of the Sphere. 

CIRCLES OF THE SPHERE. 

6. The Axis of the Earth is an imaginary line, passing through 
its centre, north and south, about which its diurnal revolution is 
performed. 

The Poles of the Earth are the extremities of its axis. 

The Axis of the Heavens is the axis of the Earth produced 
both ways to the concave surface of the heavens. 

The Poles of the Heavens are the extremities of their axis. 

The Equator of the Earth is an imaginary great circle pass- 
ing round the Earth, east and west, everywhere equally distant 
from the poles, and dividing it into northern and southern hemi- 
spheres. 

The Equator of the Heavens, or Equinoctial, is the great circle 
formed on the concave surface of the heavens, by producing the 
plane of the Earth's equator. 

A plane is that which has surface but not thickness. The plane of a circle is that ima- 
ginary superficies which is bounded by the circle. 

?. The Rational Horizon is an imaginary great circle, whose 
plane, passing through the centre of the Earth, divides the hea- 
vens into two hemispheres, of which the upper one is called the 

5. What helps to facilitate the study of the heavens ? Circles ? Called what ? 
6. Axis of the Earth ? Poles? Axis of the heavens? Poles of the heavens? Equator 
of the Earth ? Equator of the heavens, or Equinoctial ? 7. Rational horizon ? Sensi- 
ble or apparent ? 



CIRCLES OF THE SPHERE. 11 

visible hemisphere, and the lower one, the invisible hemisphere. 
It is the plane of this circle which determines the rising and set- 
ting of the heavenly bodies. 

The Sensible or Apparent Horizon, is the circle which termi- 
nates our view, where the Earth and sky appear to meet. 

To a person standing on a plain, jthis circle is but a few miles in diameter. If the eye 
be elevated five feet, the radius of the sensible horizon will be less than two miles and 
three quarters; if the eye be elevated six feet, it will be just three miles. The observer 
being always in the centre of the sensible horizon, it will move as he moves, and enlarge 
or contract, as his station is elevated or depressed. 

8. The Poles of the Horizon are two points, of which the one is 
directly overhead, and is called the Zenith ; the other is directly 
underfoot, and is called the Nadir. 

Vertical Circles are circles drawn through the Zenith and 
Nadir of any place, cutting the horizon at right angles. 

The Prime Vertical is that which passes through the east and 
west points of the horizon. 

9. The Ecliptic is the plane of the Earth's orbit ; or the great 
circle which the Sun appears to describe annually among the 
stars. It crosses the Equinoctial, a little obliquely, in two oppo- 
site points, which are called the Equinoxes. The Sun rises in 
one of these points on the 21st of March ; this point is called 
the Vernal Equinox. It sets in the opposite point on the 23d 
of September ; this point is called the Autumnal Equinox., One 
half of the Ecliptic lies on the north side of the Equinoctial, the 
other half on the south side, making an angle with it of 23|-°. 
This angle is called the obliquity of the Ecliptic. The axis of 
the Ecliptic makes the same angle with the axis of the heavens; 
so that the poles of each are 23^-° apart. 

This angle is perpetually decreasing. At the commencement of the Christian era, it 
was about 23° 45'. At the beginning of 1836, it was only 23° 27' 38", showing an annual 
diminution of about half a second, or 45". 70 in a hundred years. A time will arrive, 
however, when this angle, having reached its minimum, will again increase in the same 
ratio that it had before diminished, and thus it will continue to oscillate at long periods, 
between certain limits, which are said to be comprised within the space of 20° 42'. 

10. The Ecliptic, like every other circle, contains 360°, and it 
is divided into 12 equal arcs of 30° each, called signs, which the 
ancients distinguished by particular names. This division com- 
mences at the vernal equinox, and is continued eastwardly round 
to the same point again in the following order : Aries, Taurus, 
Gemini, Cancer, Leo, Virgo, fcibra, Scorpio, Sagittarius, Capri- 

8. Poles of the horizon? Vertical circles? Prime Vertical? 9. Ecliptic? Equi- 
noxes? How is the Ecliptic situated with respect to the Equinoctial? Obliquity of 
Ecliptic? Is this angle permanent? 10. How is the Ecliptic divided? Wli ere com- 
menced, and how reckoned? Name signs in order? How does the Sun proceed through 
the signs? 

1* 



12 ASTRONOMY. 

comus, Aquarius, Pisces. The Sun, commencing at the first 
degree of Aries, about the 21st of March, passes, at a mean 
rate, through one sign every month. 

11. The Zodiac is a zone or girdle, about 16 degrees in breadth, 
extending quite round the heavens, and including all the heavenly 
bodies within 8° on each side of the ecliptic. It includes, also, 
the orbits of all the planets, except some of the asteroids, since 
they are never seen beyond 8° either north or south of the ecliptic. 

12. Parallels of Latitude are small circles imagined to be 
drawn on the Earth's surface, north and south of the equator, 
and parallel to it. 

Parallels of Declination are small circles, imagined to be drawn 
on the concave surface of the heavens, north and south of the 
equinoctial, and parallel to it ; or they may be considered as 
circles formed by producing the parallels of latitude to the 
heavens. 

13. The Tropic of Cancer is a small circle, which lies 23-J- 
north of the Equinoctial, and parallel to it. The Tropic of 
Capricorn is a small circle, which lies 23^-° south of the Equi- 
noctial, and parallel to it. On the celestial sphere, these two 
circles mark the limits of the Sun's farthest declination, north 
and south. On the terrestrial _sphere, they divide the torrid from 
the two temperate zones. That point in the ecliptic which 
touches the tropic of Cancer, is called the Summer Solstice ; and 
that point in the ecliptic which touches the tropic of Capricorn, 
is called the Winter Solstice. 

The distance of these two points from the equinoctial, is always equal to the obliquity 
of the ecliptic, which, in round numbers, is 23c° ; but, as we have seen, the obliquity of 
the ecliptic is continually changing; therefore the position of the tropics must make a 
correspondent change. 

14. The Colures are two great circles which pass through the 
poles of the heavens, dividing the ecliptic into four equal parts, 
and mark the seasons of the year. One of them passes through 
the equinoxes at Aries and Libra, and is thence called the Equi- 
noctial Colure; the other passes through the solstitial points or 
the points of the Sun's greatest declination north and south, and 
is thence called the Solstitial Colure. 

The Sun is in the equinoctial points the 21st of March and the 23d of September. He 
is in the solstitial points the 22d of June and the 22d of December. 

15. The Polar Circles are two small circles, each about 66|-° 



11. What is the Zodiac? 12. Parallels of latitude? Of declination? 13. The 
tropics? Cancer? Capricorn? What do these circles mark in the celestial sphere? 
On the terrestrial ? 14. The Colures ? Where situated ? When is the Sun at the equi- 
noctial points ? The solsticial? 15. What are the Polar Circles? 



CIRCLES OF THE SPHERE. 13 

from the equator, being always at the same distance from the poles 
that the tropics are from the equator. The northern is called 
the Arctic circle, and the southern the Antarctic circle. 

16. Meridians are imaginary great circles drawn through the 
poles of the world, cutting the equator and the equinoctial at 
right angles. 

Every place on the Earth, and every corresponding point in the heavens, is considered 
as having a meridian passing through it; although astronomers apply but 24 to the 
heavens, thus dividing the whole concave surface into 24 sections, each 15° in width. 
These meridians mark the space which the heavenly bodies appear to describe, every 
hour, for the 24 hours of the day. They are thence sometimes denominated Hour Circles. 

In measuring distances and determining positions on the Earth, the equator and some 
fixed meridian, as that of Greenwich, contain the primary starting points ; in the hea- 
vens these points are in the ecliptic, the equinoctial, and that great meridian which 
passes through the first point of Aries, called the equinoctial colure. 

17. Latitude on the Earth, is distance north or south of the 
equator, and is measured on the meridian. 

Latitude in the Heavens, is distance north or south of the eclip- 
tic, and at right angles with it. 

Longitude on the Earth, is distance either east or west from 
some fixed meridian, measured on the equator. 

Longitude in the Heavens, is distance east from the first point 
of Aries, measured on the ecliptic. 

18. Declination is the distance of a heavenly body either north 
or south of the equinoctial, measured on a meridian. 

Right Ascension is the distance of a heavenly body east from 
the first point of Aries, measured on the equinoctial. 

It is more convenient to describe the situation of the heavenly bodies by their decli- 
nation and right ascension, than by their latitude and longitude, since the former cor- 
responds to terrestrial latitude and longitude. 

Latitude and declination may extend 90° and no more. Terrestrial longitude may 
extend 180° either east or west; but celestial longitude and right ascension, being reck- 
oned in only one direction, extend entirely round the circle, or 360°. 

It is easy to convert right ascension into time, or time into right ascension, for if a 
heavenly body is one hour in passing over 15°, it will be one fifteenth of an hour, or four 
minutes, in passing over 1°. 

If the first point of Aries be on the meridian at 12 o'clock, the next hour line, which 
is 15° E. of it, will come to the meridian at 1 o'clock; the second hour line at 2 o'clock; 
the third at 3, &c. Of any two bodies whose right ascensions are given, that one will 
pass the meridian first which has the least right ascension. 

19. In consequence of the Earth's motion eastward in its 
orbit, the stars seem to have a motion westward, besides their 
apparent diurnal motion caused by the Earth's revolution on its 
axis ; so that they rise and set sooner every succeeding day by 
about four minutes, than they did on the preceding. This is 

16. Meridians? How many? What other name? How measure distances on the 
earth? In the heavens? 17. What is latitude on the earth? In the heavens? 
Longitude on the earth? In the heavens? 13. Declination ? Right ascension? 
Why describe by D. and R. A.? Extent of latitude? Declination? Longitude and R. 
A ? How convert R. A. into time? Which of two bodies given will first pass the meri- 
dian? 19. What apparent motion of stars? Cause? Results? 



14 ASTRONOMY. 

called their daily acceleration. It amounts to just two hours a 
month. On this account we have not always the same constel- 
lations visible to us throughout the year. While some, that were 
not visible before, are successively rising to view in the east, and 
ascending to the meridian, others sink beneath the western 
horizon, and are seen no more, until, having passed through the 
lower hemisphere, they again reaopear in the east. 



DESCRIPTION AND USE OF THE MAPS. 

20. The first map of the atlas represents, upon a large scale, 
a general view of the solar system. This will be more fully 
described in the second part of the work. 

The next six maps represent different sections of the concave 
surface of the heavens. The first of these exhibits the principal 
constellations visible to us in October, November, and Decem- 
ber ; the second, those visible in January, February, and March ; 
the third, those visible in April, May, and June ; and the fourth, 
those visible in July, August, and September ; with the excep- 
tion, however, of the constellations which lie beyond the 50th 
degree of north and south declination, of which, indeed, those 
around the North Pole are always, and those around the South 
Pole, never visible to us. 

21. These constellations are represented on the sixth and 
seventh maps, called circumpolar maps, which are an exact con- 
tinuation of the others, and if joined to them at their correspond- 
ing degrees of right ascension and declination, they might be 
considered as constituting one map. The scale on which all the 
above-mentioned maps are drawn is that of a 16-inch globe. 
The lines drawn on the maps have been already defined ; and 
their use, being nearly the same with those in geography, will 
be readily understood. Those which are drawn from right to 
left, on each side of the equinoctial and parallel to it, are called 
Parallels of Declination. Those which are drawn up and down 
through the maps, at intervals of 15°, are called Meridians of 
Right Ascension, or Hour Circles. 

The scale at the top and bojttom of the first four maps, and in the circumference of 
the circumpolar maps, indicates the daily progress of the stars in right ascension, and 
shows on what day of the month any star will be on the meridian at 9 o'clock in th« 
evening. 



20. What said of maps? First? Next six? 21. Sixth and seventh? Scale? 
Pescrib© lines ? Scale indicates what ? 



CLASSIFICATION OF STARS, NEBLL^E, ETC. 15 

22. The first four maps of the heavens are so constructed 
that the pupil in using them must suppose himself to face the 
south, and to hold them directly overhead in such manner that 
the top of the map shall be towards the north, and the bottom 
towards the south ; the right hand side of the map will then be 
west, and the left-hand east. In using the circumpolar maps he 
must suppose himself to face the pole, and to hold them in such 
a manner that the day of the given month shall be uppermost. 

The constellation called the Great Bear is an exception to this rule ; in this constel- 
lation the principal stars are marked in the order of their right ascension. 

That point of projection for the maps which would exhibit each successive portion of 
the heavens directly overhead at 9 o'clock in the evening, was chosen, because in sum- 
mer at an earlier hour the twilight would bedim our observation of the stars, and at 
other seasons of the year it is easier to look up to stars that want an hour of their 
meridian altitude than to those which are directly overhead. 



CLASSIFICATION OF STARS, NEBULiE, Ac. ' 

23. For purposes of convenience in finding or referring to par- 
ticular stars, recourse is had to a variety of artificial methods 
of classification. First, the whole concave of the heavens is 
divided into sections or groups of stars, of greater or less extent, 
called Constellations. — (Of the origin of these figures see page 
143). Next, they are classified according to their magnitudes, 
(as already stated art. 4), and designated on the maps accord- 
ingly. Thirdly, the stars of each constellation are classified 
according to their magnitudes in relation to each other, and with- 
out reference to other constellations. Thus, for instance, the 
largest star in Taurus is marked a, Alpha ; the next largest (3, 
Beta; the next, y, Gamma, &c, till the Greek alphabet is 
exhausted. Then the Roman (or English) is taken up, and 
finally, if necessary, recourse is had to figures. 

This useful method of designating particular stars by the use of the Greek and Roman 
alphabet, was invented by John Bayer, of Augsburg, in Germany, in 1603. It has been 
adopted by all succeeding astronomers, and extended by the addition of the Arabic 
notation 1, 2, 3, &c, wherever the stars in a constellation outnumber both alphabets. 

As Greek letters so frequently occur in catalogues and maps of the stars and on the 
celestial globes, the Greek alphabet is here introduced for the use of those who are 
unacquainted with it. The capitals are seldom used for designating- the stars, but are 
here given for the sake of regularity. 



22. How use the first four maps of the heavens? Circumpolar? What exception? 
What point of projection chosen, and why? 23. Classification or designation of 
stars ? By whom invented, and when? 



I 16 ASTRONOMY. 

THE GREEK ALPHABET. 



A 


a 


Alpha 


N 


V 


Nu 


B 


P 


Beta 


£J 


1 


Xi 


r 


7 


Gamma 








micron 


A 


6 


Delta 


n 


7Z 


Pi 


E 


e 


Epsilon 


p 


P 


ftho 


Z 


s 


Zeta 


s 


f 


Sigma 


H 


V 


Eta 


T 


r 


Tau 





6 


Theta 


T 


■y 


Upsilon 


I 


l 


Iota 


$ 





Phi 


K 


K 


Kappa 


X 


a: 


Chi 


A 


A 


Lambda 


* 


V» 


Psi 


M 


^ 


Mu 


Q 


0) 


Omega 



24. As a further aid in finding particular stars, and especially 
in determining their number, and detecting changes, should any 
occur, catalogues of the stars have been constructed, one of 
which is over two thousand years old. Several of the principal 
stars have specific names, like the planets, as Sirius, Aldebaran, 
Regwlus, &c. 

25. The stars are still further distinguished, as single, double, 
triple, multiple, binary, variable, new, and nebulous. 

A single star is one that appears as a unit under the most 
powerful telescopes. Double, triple, and multiple stars, are those 
that appear single to the naked eye, but by the aid of telescopes 
are found to consist of two or more stars. Binary stars are 
double stars revolving around each other, often called Binary 
Systems. Variable stars are those that are found to undergo 
certain fluctuations in their brightness, sometimes becoming quite 
invisible. In most cases these changes are periodical and 
regular, on which account they are called Periodical stars. 
New stars are those that suddenly blaze forth in some portion 
of the heavens previously void. Nebulous stars are those which 
are surrounded by a faint nebula, or halo of light or mist. 

26. A cluster of stars is an assemblage or group, thrown 
promiscuously together, like the Pleiades and Hyades in Taurus, 
and the Bee Hive in Cancer. A Nebula is a cluster so remote 
as to appear only like a faint cloud or haze of light. Resolvable 
Nebulce, are those that can be resolved into distinct' stars by the 
aid of a telescope. Irresolvable Nebulce are those that have not 



24. What further aid? Age? Names of stars? 25. Stars, how further distin- 
guished? Single stars? Double, &c? Binary? What other name? Variable stars? 
What other name and why? New stars? Nebulous? 26. What are clusters? Nebu- 
las? Resolvable Nebul S3? Irresolvable ? Annular? Planetary? 



CLASSIFICATION OF STARS, NEBULA, ETC. 17 

as yet been thus resolved. Annular Nebula are those that have 
the form of an annulus or ring. Planetary Nebula are those 
that resemble planets in form, and in the sharpness of their out- 
line. Stellar Nebula are those with a star in the centre, the 
same as nebulous stars, already described (25). 

A more detailed account of the double stars, clusters and nebulse, will be given after 
the student has become somewhat familiar with the constellations. 

2*1. We may now imagine the pupil ready to begin the study 
of the visible heavens. The first thing of importance is to fix 
upon the proper starting point. This, on many accounts, would 
seem to be the North Polar Star. Its position is apparently 
the same every hour of the night throughout the year, while the 
other stars are continually moving. Many of the stars also in 
that region of the skies never set, so that when the sky is clear, 
they may be seen at any hour of the night. They revolve about 
the pole in small circles, and never disappear below the horizon, 

On this account they are said to be within the circle of perpetual apparition. On the 
other hand, the identity of the North Polar Star, strange as it may appear, is not so 
easily determined by those who are just entering upon this study, ^s that of some others. 
For this reason, the point directly overhead, called the zenith, is preferable, since upon 
this point every one can fix with certainty in whatever latitude he may be. It will be 
alike to all the central point of the visible heavens, and to it the pupil will learn imper- 
ceptibly to refer the bearing, motion, and distances of the heavenly bodies. 

That meridional point in each map, whose declination corresponds with the latitude 
of the place of observation, represents the zenith of the heavens at that place ; and 
those constellations of stars which occupy this position on the maps, will be seen directly 
overhead at 9 o'clock in the evening of the day through which the meridian passes. 
Thus in Georgia, for instance, the starting point should be those stars which are situated 
in this meridian near the 33d degree of north declination, while in New England it 
should be those which are situated in it near the 42d degree. 

28. We might, however, begin with the stars near either of 
the meridians represented on the maps, the only rule of selection 
being to commence at that which approaches nearest to being 
overhead at the time required. We have chosen for our starting 
point in this work that meridian which passes through the vernal 
equinox at the first point of Aries, not only because it is the 
meridian from which the distances of all the heavenly bodies are 
measured ; but especially because the student will thus be 
enabled to observe and compare the progressive motion of the 
constellations according to the order in which they are always 
arranged in catalogues, and also to mark the constellations of 
the Zodiac passing overhead as they rise one after another in 
their order, and to trace among them the orbits of the Earth 
and of the other planets. 

27. What first important in commencing study of the heavens? What star would 
seem best starting point? Why? Why not the best? What point preferable, and 
why? Illustration from map. 28. With what staz-s might we begin? What meridian 
thosen by the author ? Why? 



PART I. 
THE CONSTELLATIONS 



CHAPTER I. 

CONSTELLATIONS ON THE MERIDIAN IN NOVEMBER. 

ANDROMEDA.— MAP V.* 

29. If we look directly overhead at 10 o'clock, on the 10th 
of November, we shall see the constellation celebrated in fable 
by the name of Andromeda. It is represented on the map by the 
figure of a woman having her arms extended, and chained by 
her wrists to a rock. It is bounded N. by Cassiopeia, E. by 
Perseus and the head of Medusa, and S. by the Triangles and 
the Northern Fish. It is situated between 20° and 50° of N. 
declination. Its mean right ascension is nearly 15°; or one 
hour E. of the equinoctial colure. 

30.; It consists of 66 visible stars, of which three are of the 2d 
magnitude, and two of the 3d ; most of the rest are small. The 
stars directly in the zenith are too small to be seen in the pre- 
sence of the moon, but the bright star Almaack (y), of the 2d 
magnitude, in the left foot, may be seen 13° due E., and Merach 
(]3), of the same magnitude, in the girdle 7° south of the 
zenith. This star is then nearly on the meridian, and with two 
others N.W. of it forms the girdle. 

The three stars forming the girdle are of the 2d, 3d, and 4th 
magnitude, situated in a row, 3° and 4° apart, and are called 
Merach, Mu, and Nu. 

31. If a straight line, connecting Almaack with Merach, be 

* As the eastward motion of the earth in her orbit causes the sun to pass eastward 
annually around the heavens, and the constellations to rise earlier and earlier (19), the 
student will find it necessary to proceed eastward around the heavens, in studying the 
constellations. And as the right hand of the map is west, and the left hand east, we 
begin with the equinoctial colure, map II., and proceed to the left in the order in which 
the constellations successively arise. 

29. What constellation? Maps, and why? (Note.) How Andromeda represented? 
Boundaries? Situation? Right ascension and declination? 30. Number of stars ? 
Magnitude? Almaack? Merach? "Girdle?" 31. Situation of Delta? Magnitude? 
How otherwise known? Alpheratz? Substance of note (fine print) ? 



ANDROMEDA. 19 

produced south-westerly, 8° farther, it will reach to (6) Delta, 
a star of the 3d magnitude in the left breast. This star may be 
otherwise known by its forming a line, N. and S., with two 
smaller ones on either side of it ; or, by its constituting, with 
two others, a very small triangle, S. of it. 

Nearly in a line with Almaack, Merach and Delta, but curv- 
ing a little to the N. 1° farther, is a lone star of the 2d magni- 
tude, in the head, called Alpheratz (a). This is the KE. cor- 
ner of the great " Square of Pegasus," to be hereafter described. 

It will be well to have the position of Alpheratz well fixed in the mind, because it is 
but one minute west of the great equinoctial colure, or first meridian of the heavens, 
and forms nearly a right line with Algenib, in the wing of Pegasus, 14° S. of it, and with 
Beta in Cassiopeia, 30° N. of it. If a line, connecting these three stars, be produced, it 
will terminate in the pole. These three guides, in connection with the North Polar Star, 
point out to astronomers the position of that great circle in the heavens from which the 
right ascension of all the heavenly bodies is measured. 

MYTHOLOGICAL HISTORY. 

32. The story of Andromeda, from which this constellation derives its name, is as follows: 
She was daughter of Cepheus, King of Ethiopia, by Cassiopeia. She was promised in 
marriage to Phineus, her uncle, when Neptune drowned the kingdom, and sent a sea 
monster to ravage the country, to appease the resentment which his favorite nymphs 
bore against Cassiopeia, because she had boasted herself fairer than Juno and the 
Nereides. The oracle of Jupiter Ammon was consulted, and nothing could pacify the 
anger of Neptune unless the beautiful Andromeda should be exposed to the sea monster. 
She was accordingly chained to a rock for this purpose, near Joppa (now Jaffa, in Syria), 
and at the moment the monster was going to devour her, Perseus, who was then return- 
ing through the air from the conquest of the Gorgons, saw her, and was captivated by 
her beauty. 

"Chained to a rock she stood ; young Perseus stay'd 
His rapid flight, to woo the beauteous maid." 

He promised to deliver her and destroy the monster if Cepheus would give her to 
him in marriage. Cepheus consented, and Perseus instantly changed the sea monster 
into a rock, by showing him Medusa's head, which was still reeking in his hand. The 
enraged Phineus opposed their nuptials, and a violent battle ensued, in which he, also, 
was turned into a stone, by the petrifying influence of the Gorgon's head. 

The morals, maxims, and historical events of the ancients, were usually communicated 
in fable or allegory. The fable of Andromeda and the sea monster might mean that she 
was courted by some monster of a sea-captain, who attempted to carry her away, but 
was prevented by another more gallant and successful rival. 

TELESCOPIC OBJECTS. 

33. Under the head of Telescopic Objects, will be included clusters and nebulae that 
are visible to the naked eye, as well as the principal objects of interest that are strictly 
telescopic. In describing the location of these objects, R. A. will denote Bight Ascen- 
sion; and Dec, Declination. The initials N. and S. will indicate whether the 
declination is North or South of the equinoctial. 

In describing the location of the telescopic object, the R. A. will be given in time ; 
viz., in hours, minutes, and seconds, instead of degrees, minutes, and seconds: each 
hour answering to 15°. The hour circles are distinctly drawn on all the maps, the first 
being 15° east of the equinoGtial colure (Map II.), and so on eastward to the same point 
again. The hours will be seen marked just under the equinoctial, which is marked off 
into degrees, each of which answers to four minutes of time. The student will soon find 
it much more convenient to reckon R. A. by hours, on the maps, than by degrees, &c. 

32. History. — What may it have meant ? 

33. What included among Telescopic Objects ? What meant by R. A. ? Dec. ? N. and 
S. ? How R. A. laid down? How on map? What mode of describing components of 
double stars ? Of a Andromeda ? Of discrepancies between R. A. given, and loca- 
tion of stars on the maps ? How is R. A. given in locating objects ? Why ? How 
are hours marked on the maps ? The minutes ? 



20 



ASTRONOMY. 



34. In consequence of the perpetual recession of the equinoxes westward, the R. A. 
of objects is constantly increased by about 50" per year. It is vain, therefore, to attempt 
togxve R. A. for the time when a book will he us*d; or to construct maps that will 
show objects m their true place, for different years to come. The necessary allowance 
must be made in all cases ; so that the R. A. for one epoch is about as good as another. 
JLlie R. A. here given is from Smyth's Celestial Cycle, epoch Jan. 1, 1840. Maps should 
be re-engraved every fifty years, but for all shorter periods allowance can be made by 
the student As the maps accompanying this work were drawn and engraved in 1835, 

« Pj: esent . R - A - ( 1854 ) is about 17' or 4m. of time east of their places on the maps. 

65, lhe order in which the telescopic objects will be arranged is first the double stars ; 
secondly, clusters; and lastly the nebulas. The double stars will be classed according 
to their order in the respective constellations ; i.e., a first, R next, Ac. Thus, as the 
largest objects are first named, the student can begin with those easiest found, and 
requiring the least telescopic power ; and proceed from the easier to those more diffi- 
cult. The same plan is generally pursued with the clusters and nebulae. 

TELESCOPIC OBJECTS IN ANDROMEDA. 

1. a Andromeda (Alpheratz)— A star with a minute companion, R. A. Oh. 0m. 08s. -. 
Dec, N. 28° 12' 05". A. 1, bright white ; B. 11, purplish. On the map it is ^oest of the 
equinoctial, the map having been engraved some twenty years ; but the equinox having 
constantly receded westward, had passed Alpheratz before 1840, some 8'. Similar dis- 
crepancies between the R. A. given and the location of different stars on the map, are 
due to the same cause. 

2. R Andromeda (Merach)— A bright star with a distant telescopic companion, R. A. 
lh. 00m. 47s. ; Dec, N. 34° 46' 08". A. 2, fine yellow ; B. 12, pale blue, with several small 
stars in the field. 

3. y Andromeda {Almaack)—A splendid double star on the right foot, R. A. lh. 54m. 
36s ; Dec. N. 41° 33' 06". A. 3%, orange color ; B. 5H, emerald green. Found by a line 
from 6 to R, and about twice as far beyond. (Map VIIL, Fig. 1.) 

4. <3' Andromeda — A bright star on the right breast, with a distant telescopic com- 
panion, R. A. Oh. 30m. 47s. ; Dec, N. 29° 59' 01". A. 3, orange ; B. 11 Jg, dusky ; with the 
small stars in the southern part of the field. 

5. K Andromeda— A wide, but delicate triple star, in the northern hand; midway 
between R Pegasi and a Cassiopeia ; or about 18° from each ; R. A. 23h. 32m. 33s ; Dec, 
N. 43° 27' 0". A. 5, brilliant white; B. 14, dusky; C. 12, ash-colored. 

6. An Elongated Nebula on the lady's right foot, R. A,2h. 12m. 35s. ; Dec, N.4I° 36". 
It was discovered by Miss Caroline Herschell, in 1783. Sir William Herschell described 
it as having "a black division or chink in the middle." He regarded it as a flat ring 
of enormous dimensions, seen very obliquely. Captain Smyth says : "In my telescope 
it is certainly brighter at the edges than along the central part." See map VIII., Fig. 21. 

7. About 2° from Nu at the north-western extremity of the girdle, R. A. 00° 34m. 05s., 
N. Dec, 40° 23' 06", is a, remarkable nebula of very minute stars, and the only one of 
the kind which is ever visible to the naked eye. It resembles two cones of light, joined 
at their base, about %° in length, and i£° in breadth. It was known as far back as A.D. 
905, is of an oval shape, and is described by Smyth as " an overpowering nebula, with . 
a companion about 25' in the south vertical." Sir William Herschell considered this the 
nearest of all the great nebulas, and yet so remote that it would require 6,000 years for 
light to pass from it to our system, though flying at the rate of 190,000 miles per second ! 
Fig. 22, map VIIL, is a representation of this object. 

PISCES (the fishes).— MAP Y. 

36. This constellation is now the first in order of the twelve 
constellations of the Zodiac, and is usually represented by two 
fishes tied a considerable distance apart, at the extremities of a long 
undulating cord, or ribbon. It occupies a large triangular space 

34. What said of the change of R. A. of objects? Cause? Epoch of R. A. given in 
book? Of that marked on maps? Allowance to be made in finding objects by maps? 
35. Order in which objects are presented? Advantage of this arrangement? 

Telescopic Objects.— What double stars? a? /?? >? What clusters or nebulae? 
Shown on map, or not? 

36. Pisces? Where situated? What now called ? 



PISCES. 21 

in the heavens, and its outline at first is somewhat difficult to be 
traced. 

In consequence of the annual precession of the stars, the constellation Pisces has now 
oome to occupy the sign Aries ; each constellation having advanced one whole sign in 
the order of the Zodiac. The Sun enters the sign Pisces, while the Earth enters that of 
Virgo, about the 19th of February, but he does not reach the constellation Pisces before 
the 6th of March. The Fishes, therefore, are now called the "Leaders of the Celestial 
Hosts." — See Aries. 

3T. That loose assemblage of small stars directly south of 
Merach, in the constellation of Andromeda, constitutes the 
Northern Fish, whose mean length is about 16°, and breadth, 
1°. Its mean right ascension is 15°, and its declination 25° N. 
Consequently, it is on the meridian the 24th of November ; and 
from its breadth, is more than a week in passing over it. 

38. The Northern Fish and its ribbon, beginning at Merach, 
may by a train of small stars, be traced in a S. S. easterly direc- 
tion, for a distance of 33°, until we come to the star El Rischa, 
of the 3d magnitude, which is situated in the node, ot flexure of 
the ribbon. This is the principal star in the constellation, and 
is situated 2° N. of the equinoctial, and 53 minutes east of the 
meridian. 

Seven degrees S. E. of El Rischa, passing by three or four very small stars, we come to 
Mira, in the whale, a star of about the 3d magnitude, and known as the " Wonderful 
Star of 1596." El Rischa may be otherwise identified by means of a remarkable cluster 
of five stars in the form of a pentagon, about 15° E. of it. — See Cetus. 

39. From El Rischa the ribbon or cord makes a sudden 
flexure, doubling back across the ecliptic, where we meet with 
three stars of the fourth magnitude situated in a row 3 and 4° 
apart, marked on the map Zeta, Epsilon, Delta. From Delta 
the ribbon runs north and westerly along the Zodiac, and termi- 
nates at Beta, a star of the 4th magnitude, 11° S. of Markab 
in Pegasus. 

This part of the ribbon, including the Western Fish at the end of it, has a mean 
declination of 5° N., and maybe seen throughout the month of November, passing the 
meridian slowly to the W., near where the sun passes it on the 1st of April. 

40. Twelve degrees W. of this Fish, there are four small stars 
situated in the form of the letter Y. The two Fishes, and the 
cord between them, make two sides of a large triangle, 30° and 
40° in length, the open part of which is towards the N. W. 
When the Northern Fish is on the meridian, the Western is 
nearly two hours past it. This constellation is bounded N. by 

37. Northern Fish? Length? Dec? When on the meridian ? 38. How trace the 
Northern Fish? To what star? Magnitude? Where situated? 89. From El Rischa? 
From Delta? Mean declination of this part of the ribbon? 40. What 12° west of 
this fish? What do the two fishes, &c, make ? Boundaries of Pisces? 



22 ASTRONOMY. 

Andromeda, W. by Andromeda and Pegasus, S. by the Cascade, 
and E. by the Whale, the Ram and the Triangles. 

When, to enable the pupil to find any star, its direction from another is given, the 
latter is always understood to be on the meridian. 

After a little experience with the maps, even though unaccompanied by directions, 
the ingenious youth will be able, of himself, to devise a great many expedients and facili- 
ties for tracing the constellations, or selecting out particular stars. 

In using a circumpolar map, face the pole, and hold it up in your hands in such a 
manner that the part which contains the name of the given month shall be uppermost, 
and you will have a portraiture of the heavens as seen at that time. 

The constellations about the Antarctic Pole are not visible in the United States ; 
those about the Arctic or Northern Pole, are always visible. 

HISTORY. 

41. The ancient Greeks, who have some fable to account for the origin of almost 
every constellation, say, that as Yenus and her son Cupid were one day on the banks of 
the Euphrates, they were greatly alarmed at the appearance of a terrible giant, named 
Typhon. Throwing themselves into the river, they were changed into fishes, and by 
this means escaped danger. To commemorate this event, Minerva placed two fishes 
among the stars. 

According to Ovid, Homer, and Virgil, this Typhon was a famous giant. He had a hun- 
dred heads, like those of a serpent or dragon. Flames of devouring fire darted from his 
mouth and eyes. He was no sooner born, than he made war against heaven, and so 
frightened the gods, that they fled and assumed different shapes. Jupiter became a 
ram: Mercury, an Ibis; Apollo, a crow; Juno, a cow; Bacchus, a goat; Diana, a cat; 
Venus, a fish, &c. The father of the gods, at last, put Typhon to flight, and crushed him 
under Mount iEtna. 

The sentiment implied in the fable of this hideous monster, is evidently this : that 
there is in the world a description of men whose mouth is so "full of cursing and bitter- 
ness," derison and violence, that modest virtue is sometimes forced to disguise itself, 
or flee from their presence. 

In the Hebrew Zodiac, Pisces is allotted to the escutcheon of Simeon. 

No sign appears to have been considered of more malignant influence than Pisces. 
The astrological calendar describes the emblems of this constellation as indicative of 
violence and death. Both the Syrians and Egyptians abstained from eating fish, 
out of dread and abhorrence ; and when the latter would represent anything as odious, 
or express hatred by hieroglyphics, they painted &Jish, 

TELESCOPIC OBJECTS. 

1. a Piscium (M Rischa) — A close double star in the eastern extremity of the ribbon, 
R. A. lh. 53m. 46s. ; Dec. N. 1° 59' 03". A. 5, pale green ; B. 6, blue ; a splendid object, 
and easily found. 

2. t; Piscium — A neat double star in the ribbon, about 13° north-west of a, R. A. lh. 
5m. 23s. ; Dec. N. 6° 43' 07". A. 6, silvery white; B. 8, pale gray; a fine object. 

3. (j) Piscium — A close double star in the space between the two fishes, about half-way 
between 7j Andromeda and Ceti; R. A. lh. 2m. 31s. ; Dec. N. 8° 42'. A. 8, white; 
B. 14, pale blue. 

4. A neat double star, about 4° south of Algenih, in the wing of Pegasus, R. A. Oh. 
lm. 53s. ; Dec. N. 10° 14' 06". A. 6, silvery white ; B. 13%, pale blue. 

5. A faint nebula in the eye of the western Eish, about 10° south-half-east of Mar- 
kab, near y Piscium; R. A. 23h. 06m. 36s. ; Dec. 3° 39' V : a very difficult object. 

CASSIOPEIA.— MAP VI. 

42. Cassiopeia is represented on the celestial map in regal state, 
seated on a throne or chair, holding in her left hand the branch 

41. History?— Greek account? Ovid's and others? Sentiment or moral? Hebrew 
Zodiac? Astrology? 

Telescopic Objects.— Double stars ? Clusters? Nebulaj? Shown on map, or not? 

42. Cassiopeia? How represented? Head? 



CASSIOPEIA. 23 

of a palm tree. Her head and body are seen in the Milky Way. 
Her foot rests upon the Arctic Circle, upon which her chair is 
placed. She is surrounded by the chief personages of her royal 
family. The king, her husband, is on her right hand — Perseus, 
her son-in-law, on her left — and Andromeda, her daughter, just 
above her. 

43. This constellation is situated 26° N. of Andromeda, and 
midway between it and the North Polar Star. It may be seen 
from our latitude, at all hours of the night, and may be traced 
out at almost any season of the year. Its mean declination is 
60 p N. and its right ascension 12°. It is on our meridian the 
2 2d of November, but does not sensibly change its position for 
several days ; for it should be remembered that the apparent 
motion of the stars becomes slower and slower, as they approxi- 
mate the poles. 

44. Cassiopeia is a beautiful constellation, containing 55 stars 
that are visible to the naked eye ; of which four are of the 3d 
magnitude, and so situated as to form, with one or two smaller 
ones, the figure of an inverted chair. 

" Wide her stars 



Dispersed, nor shine with mutual aid improved; 
Nor dazzle, brilliant with contiguous flame : 
Their number fifty-five." 

45. Caph, in the garland of the chair, is almost exactly in the 
equinoctial colure, 30° N.of Alpheratz, with which, and the 
Polar Star, it forms a straight line. Caph is therefore on the 
meridian the 10th of November, and one hour past it on the 
24th. It is the westernmost star of the bright cluster. Shedir, 
in the breast, is the uppermost star of the five bright ones, and 
is 5° S. El. of Caph : the other three bright ones, forming the 
chair, are easily distinguished, as they meet the eye at the first 
glance. 

There is an importance attached to the position of Caph that 
concerns the mariner and the surveyor. It is used, in connec- 
tion with observations on the Polar Star, for determining the 
latitude of places, and for discovering the magnetic, variation of 
the needle. 

46. It is generally supposed that the North Polar Star, so 
called, is the real immovable pole of the heavens : but this is a 
mistake. It is so near the true pole that it has obtained the 

43. Situation? How seen? R. A. and Dec? When on meridian? 44. Number of 
stars? Magnitudes? Figure? Character of this constellation? 45. Caph? How 
situated? When on meridian? Shedir? Importance attached to Caph? 46. Pole 
star? Is it the true pole? What variation? How pole star situated with reference to 



24 ASTRONOMY. 

appellation of the North Polar Star ; but it is, in reality, more 
than a degree and a half distant from it, and revolves about the 
true pole every 24 hours, in a circle whose radius is 1° 31'. It 
will consequently, in 24 hours, be twice on the meridian, once 
above, and once below the pole ; and twice at its greatest elonga- 
tion E. and W. 

The Polar Star not being exactly in the N. pole of the heavens, but one degree and 
81 minutes on that side of it which is towards Caph, the position of the latter becomes 
important, as it always shows on which side of the true pole the polar star is. 

There is another important fact in relation to the position of this star. It is equidis- 
tant from the pole, and exactly opposite another remarkable star in the square of the 
Great Bear, on the other side of the pole. [See Megrez.] It also serves to mark a spot 
in the starry heavens, rendered memorable as being the place of a lost star. Two hun- 
dred and fifty years ago, a bright star shone 5° N. N. E. of Caph, where now is a 
dark void ! 

On the 8th of November, 1572, Tycho Brahe and Cornelius Gemma saw a star in the 
constellation of Cassiopeia, which became, all at once, so brilliant, that it surpassed the 
splendor of the brightest planets, and might be seen even at noonday. Gradually, 
this great brilliancy diminished, until the 15th of March, 1573, when, without moving 
from its place, it became utterly extinct. 

Its color, during this time, exhibited all the phenomena of a prodigious flame — first, 
it was of a dazzling white, then of a reddish yellow, and lastly of an ashy paleness, in 
which its light expired. It is impossible, says Mrs. Somerville, to imagine anything 
more tremendous than a conflagration that could be visible at such a distance. It was 
seen for sixteen months. Some astronomers imagined that it would reappear again 
after 150 years ; but it has never been discovered since. This phenomenon alarmed all 
the astronomers of the age, who beheld it ; and many of them wrote dissertations con- 
cerning it. 

Rev. Professor Vince, one of the most learned and pious astronomers of the age, has 
this remark : — " The disappearance of some stars may be the destruction of that system 
at the time appointed by the Deity for the probation of its inhabitants ; and the appear- 
ance of new stars may be the formation of new systems for new races of beings then 
called into existence to adore the works of their Creator." 

Thus, we may conceive the Deity to have been employed from all eternity, and thus 
he may continue to be employed for endless ages ; forming new systems of beings to 
adore him; and transplanting beings already formed into happier regions, who will con- 
tinue to rise higher and higher in their enjoyments, and go on to contemplate system 
after system through the boundless universe. 

La Place says : — As to those stars which suddenly shine forth with a very vivid light, 
and then immediately disappear, it is extremely probable that great conflagrations, pro- 
duced by extraordinary causes, take place on their surface. This conjecture, continues 
he, is confirmed by their change of color, which is analogous to that presented to us on 
the earth by those bodies which are set on fire, and then gradually extinguished. 

The late eminent Dr. Good also observes that — Worlds, and systems of worlds, are not 
only perpetually creating, but also perpetually disappearing. It is an extraordinary fact, 
that within the period of the last century, not less than thirteen stars, in different con- 
stellations, seem to have totally perished, and ten new ones to have been created. In 
many instances it is unquestionable, that the stars themselves, the supposed habitation 
of other kinds or orders of intelligent beings, together with the different planets by 
which it is probable they were surrounded, have utterly vanished, and the spots which 
they occupied in the heavens have become blanks ! What has befallen other systems will 
assuredly befall our own. Of the time and the manner we know nothing, but the fact is 
incontrovertible ; it is foretold by revelation ; it is inscribed in the heavens ; it is felt 
through the earth. Such is the awful and daily text ; what then ought to be the comment? 

The great and good Beza, falling in with the superstition of his age, attempted to prove 
that this was a comet, or the same luminous appearance which conducted the magi, or 
wise men of the East, into Palestine, at the birth of our Saviour, and that it now appeared 
to announce his second coming. 

Caph ? What other important fact in relation to the position of Caph ? What remark- 
able fact stated? By whom attested? Describe phenomenon? Mrs. Somerville's 
remark? Other astronomers'? Professor Vince's remarks? The author's? La 
Place's ? Dr. Good's ? Beza's ? 



CEPHEUS. 25 

HISTORY. 

Cassiopeia was the wife of Cepheus, King of Ethiopia, and mother of Andromeaa. She 
was a queen of matchless beauty, and seemed to be sensible of it ; for she even boasted 
herself fairer than Juno, the sister of Jupiter, or the Nereides — a name given to the sea- 
nymphs. This so provoked the ladies of the sea, that they complained to Neptune of the 
insult, who sent a frightful monster to ravage her coast, as a punishment for her inso- 
lence. But the anger of Neptune and the jealousy of the nymphs were not thus appeased. 
They demanded, and it was finally ordained that Cassiopeia should chain her daughter 
Andromeda, whom she tenderly loved, to a desert rock on the beach, and leave her 
exposed to the fury of this monster. She was thus left, and the monster approached ; 
but just as he was going to devour her, Perseus killed him. 
" The saviour* youth the royal pair confess. 
And with heav'd hands, their daughter's bridegroom bless." 

Uusden's Ovid. 

TELESCOPIC OBJECTS. 

1. a CassiopEjE {Shedir) — A bright star, with a companion in the bosom of the figure ; 
R. A. Oh. 31m 29s. ; Dec. 65° 39' 05". A 3, pale rose tint; B 10%, small blue. Smyth 
and Herschell note Shedir as variable. 

2. [3 Cassiopeje (Cap7i) — A bright star on the left side, with a- minute companion ; 
R. A. Oh. 0m. 42s.; Dec. N. 5S° 16' 03". A 2%, whitish; B 11%, dusky. Look directly 
opposite Megris, in the great dipper, through the pole star, and about as far beyond. 

3. y Cassiope.e — A bright star with a distant companion on the right side of the figure ; 
R. A. Oh. 47m. 05s. ; Dec. N. 59° ,50' 08". A 3, brilliant white ; B 13, blue. Many small 
stars in the field. 

4. r/ Cassiope^e — A binary star, about 4° from a towards Polaris ; R. A. Oh. 39m. 27s. ; 
Dec. N. 56° 57' 09". A. 4, pale white ; B. 7%, purple. Estimated period 700 years. 

5. ju Cassiope.<e — A coarse triple star in the right elbow ; R. A. Oh. 57m. 23s. ; Dec. N. 
54° 08' 01". A 5%, deep yellow ; B 14, pale blue ; C 11, bluish. Several small stars in the 
field. 

6. a Cassiope^e — A beautiful double star in the left elbow ; R. A. 23h. 50m. 55s. ; Dec. 
N. 54° 51' 08". A 6, flushed white ; B 8, smalt blue ; the colors clear and distinct. 

7. A coarse quadruple star, just south of Cepheus' right hand ; or about 27° south- 
aouth-west of Polaris, on a line drawn over y Cephei. R. A. 23h. 17m. 45s. ; Dec. N. 64° 
24' 03". A 5, pale yellow ; B 9, yellowish ; C 11, and D, 13, both blue. 

8. A large and straggling cluster, between the footstool of Cassiopeia and the head of 
Cepheus ; R. A. Oh. 18m. 10s. ; Dec. N. 70° 30' 08". A line from y Cassiopese, % the dis- 
tance to y Cephei, will fall upon this object. A coarse double star in the field. 

9. A rich, but somewhat straggling cluster; R. A. Oh. 24m. 5s.; Dec. N. 62° 23' 09". 
Vicinity splendidly strewed with stars — a double star in the centre. Look near the 
star «.- 

10. A loose cluster, including a small double star ; R. A. Oh. 34m. 15s. ; Dec. N. 60° 
54' 07". A 8%, B 11, both pale. Situated just half way between y and #. 

11. A loose cluster of small stars ; R. A. Oh. 5Sm. 19s. ; Dec. N. 60° 44'. On a line from 
y towards g, about % the distance. 

12. A cluster and neat double star on a line from a through J, and about 2%° beyond. 
In an elegant field of large and small stars. 

13. A fine galaxy Cluster of minute stars, about 3° south-west of /3, and about the 
same distance west of a. R. A. 23h. 49m. 07s. : Dec. N. 55° 49' 06". A glorious assem- 
blage, both in extent and richness. Resembles a crab, having spangled rays of stars, 
spreading over many fields. Map YIIL, Fig. 23. 



CEPHEUS.— MAP YI. 

4*7. Cepheus is represented on the map as a king, in his royal 
robe, with a sceptre in his left hand, and a crown of stars upon 

History? — Who was Cassiopeia? Personal appearance ? Sad consequences ? Rescue? 
Telescopic Objects.— Double and multiple stars ? Clusters ? What shown on map ? 
47. How is Cepheus represented? Where situated? 



26 ASTRONOMY. 

his head. He stands in a commanding posture, with his left 
foot over the pole, and his sceptre extended towards Cassiopeia, 
as if for favor and defence of the queen. 

" Cepheus illumes 
The neighboring heavens ; still faithful to his queen, 
With thirty-five faint luminaries mark'd." 

This constellation is about 26° N. W. of Cassiopeia, near the 2d coil of Draco, and is on 
the meridian at 8 o'clock the 3d of November ; but it will linger near it for many days. 
Like Cassiopeia, it may be seen at all hours of the night, when the sky is clear, for to us it 
never sets. 

By reference to the lines on the map, which all meet in the pole, it will be evident that 
a star, near the pole, moves over a much less space in one hour, than one at the equi- 
noctial ; and generally, the nearer the pole, the narrower the space, and the slower 
the motion. 

The stars that are so near the pole may be better described by their polar distance, 
than by their declination. By polar distance is meant, the distance from the pole, and 
is what the declination wants of 90°. 

48. In this -constellation there are 35 stars visible to the 
naked eye ; of these, there glitters on the left shoulder, a star 
of the 3d magnitude, called Alderamin, which with two others of 
the same brightness, 8° and 12° apart, form a slightly curved 
line towards the N. E. The last, whose letter name is Gamma, 
is in the right knee, 19° N. of Caph, in Cassiopeia. The middle 
one in the line is Alphirk, in the girdle. This star is one-third 
of the distance from Alderamin to the pole, and nearly in the 
same right line. 

It cannot be too well understood that the bearings, or direction of one star from 
another, as given in this treatise, are strictly applicable only when the former one is on, 
or near the meridian. The bearings given, in many cases, are not the least approxima- 
tions to what appears to be their relative position ; and in some, if relied upon, will lead 
to errors. For example : — It is said in the preceding paragraph, that Gamma, in Cepheus, 
bears 19° N. of Caph in Cassiopeia. This is true, when Caph is on the meridian, but at 
this very moment, while the author is writing this line, Gamma appears to be 19° due 
west of Caph; and six months hence, will appear to be the same distance east of it. 
The reason is obvious ; the circle which Cepheus appears to describe about the pole, is 
within that of Cassiopeia, and consequently when on the east side of the pole, will be 
within, or between Cassiopeia and the pole — that is, west of Cassiopeia. And for the 
same reason, when Cepheus is on the west side of the pole, it is between that and Cassio- 
peia, or east of it. 

Let it also be remembered, that in speaking of the pole, which we shall have frequent 
occasion to do, in the course of this work, the North Polar Star or any imaginary point 
very near it, is always meant ; and not, as some will vaguely apprehend, a point in the 
horizon, directly N. of us. The true pole of the heavens is always elevated just as many 
degrees above our horizon, as we are north of the Equator. If we live in 42° N. latitude, 
the N. pole will be 42° above our horizon. {See North Polar Star.) 

49. There are also two smaller stars about 9° E. of Aldera- 
min and Alphirk, with which they form a square ; Alderamin 
being the upper, and Alphirk the lower one on the W. 8° apart. 
In the centre of this square there is a bright dot, or semi-visible 
star. 

The head of Cepheus is in the Milky-Way, and may be known 

48. Number of stars visible ? Principal stars ? Situation ? 49. What other stars, 
and situation ? Situation of the Juead, and how known ? Distance of this Asterism from 
the pole star ? 



CEPHEUS. 27 

by three stars of the 4th magnitude in the crown, which form a 
small acute triangle, about 9° to the right of Alcleramin. The 
mean polar distance of the constellation is 25°, while that of 
Alderamin is 28° 10'. The right ascension of the former is 
338° ; consequently, it is 22° E. of the equinoctial colure. 

The student will understand that right ascension is reckoned on the equinoctial, from 
the first point of Aries, E., quite round to the same point again, which is 360°. Now, 
838* measured from the same point, will reach the same point again, within 22° ; which is 
the difference between 83'J° and 333°. This rule will apply to any other case. 

HISTORY. 

This constellation immortalizes the name of the king of Ethiopia. The name of his 
queen was Cassiopeia. They were the parents of Andromeda, who was betrothed to 
Perseus. Cepheus was one of the Argonauts who accompanied Jason on his perilous 
expedition in quest of the golden fleece. Newton supposes that it was owing to this 
circumstance that he was placed in the heavens ; and that not only this, but all the 
ancient constellations, relate to the Argonautic expedition, or to persons some way con- 
nected with it. Thus, he observes, that as Musaeus, one of the Argonauts, was the first 
Greek who made a celestial sphere, he would naturally delineate on it those figures which 
had some reference to the expedition. Accordingly, we have on our globes to this day, 
the Golden Earn, the ensign of the ship in which Phryxus fled to Colchis, the scene of 
the Argonautic achievements. We have also the Bull with brazen hoofs, tamed by 
Jason ; the Twins, Castor and Pollux, two sailors, with their mother Leda, in the form 
of a Swan, and Argo, the ship itself; the watchful Dragon, Hydra, with the Cup of 
Medea, and a raA'en upon its carcase, as an emblem of death ; also Chiron, the Master 
of Jason, with his Altar and Sacrifice; Hercules, the Argonaut, with his club, his dart, 
and vulture, with the dragon, crab, and lion which he slew; and Orpheus, one of the 
company, with his harp. All these, says Newton, refer to the Argonauts. 

Again ; we have Orion, the son of Neptune, or, as some say, the grandson of Mines, 
with his dogs, and hare, and river, and scorpion. We have the story of Perseus in the 
constellation of that name, as well as in Cassiopeia, Cepheus, Andromeda, and Cetus ; 
that of Calisto and her son Areas, in Ursa Major ; that of Icarius, and his daughter 
Erigone, in Bootes and Virgo. Ursa Minor relates to one of the nurses of Jupiter; 
Auriga, to Erichtonius ; Ophiuchus, to Phorbas ; Sagittarius, to Crolus, the son of one 
of the Muses ; Capricorn, to Pan, and Aquarius to Ganymede. We have also Ariadne's 
croicn, Bellerophon's horse, Neptune's dolphin, Ganymede's eagle, Jupiter's goat, with 
her kids, the asses of Bacchus, the fishes of Tenus and Cupid, with their parent, the 
southern fish. These, according to Deltoton, comprise the Grecian constellations men- 
tioned by the poet Aratus ; and all relate, as Newton supposes, remotely or immediately 
to the Argonauts. 

It may be remarked, however, that while none of these figures refer to any transactions 
of a later date than the Argonautic expedition, yet the great disagreement which appears 
in the mythological account of them, proves that their invention must have been of 
greater antiquity than that event, and that these constellations were received for some 
time among the Greeks, before their poets referred to them in describing the particulars 
of that memorable expedition. 

TELESCOPIC OBJECTS. 

1. a Cephei (Alderamin) — A fine star, with a distant companion on the left shoulder 
of Cepheus; R. A., 21h. 15m. ; Dec, 61° 54'. It is about half way between Polaris and 
Deneb, and 8° south-west from fi Cephei. A 3, white ; B 10, pale blue, with a companion 
of the same magnitude and color. 

2. /3 Cephei (Alphirk)—k. double star on the left side of the girdle of Cepheus, two- 
thirds of the distance from Polaris to Alderamin. A 3, white ; B 8, blue, with a very 
minute double star preceding. 

3. y Cephei (Er Bai)—A double star in the knee of Cepheus, with a distant telescopic 
companion on the preceding parallel. A 3, yellow ; B 14, dusky. R. A., 23h. 32m. 47s. ; 
Dec, N. 76° 44' V. This star will be the Pole star in about 2360 years. 

History.— Who was Cepheus ? Why placed in the heavens ? What said of the origin 
of other constellations? 
Telescopic Objects.— Alpha ? Beta, &c? What clusters ? 

B.G. 2 



28 ASTRONOMY. 

4. 6 Cephei ( Var) in the crown of Cepheus, a fine, though wide double star ; K. A. 22h, 
23m. 14s. ; Dec, N. 57° 35' 9". A 4>g, orange tint; B 7, fine blue— the colors in fine con- 
trast. This star is variable, with a period of 5d. 8h. 30m. 

5. A large and rich cluster on the left elbow ; R. A., 20h. 28m. 17s. ; Dec, N. 60* Oft' 
2". It is 12° due north of a Cygni; and 3° west-south-west of rj Cephei. "A graod but 
distant collocation of suns bound together by mutual relations." 

6. An irregular cluster between the head of Cepheus and the chain of Andromeda ; 
R. A., 23h. 17m. 10s. ; Dec, N. 60° 43' 1". It is about one-third of the distance from 
8 Cassiopeas to a Cephei ; and may be seen on Map VI., near the sceptre of Cepheua. 
For a telescopic view, see Map VIII., Fig. 24. 



CHAPTER II. 

CONSTELLATIONS ON THE MERIDIAN IN DECEMBER. 
AEIES (THE RAM).— MAP II. 

50. Twenty-two centuries ago, as Hipparchus informs us, 
this constellation occupied the first sign in the ecliptic, com- 
mencing at the vernal equinox. But as the constellations gain 
about 50" on the equinox, at every revolution of the heavens,* 
they have advanced in the ecliptic nearly 31° beyond it, or more 
than a whole sign : so that the Pishes now occupy the same 
place in the Zodiac, that Aries did in the time of Hipparchus ; 
while the constellation Aries is now in the sign Taurus, Taurus 
in Gemini, and Gemini in Cancer, and so on. 

Aries is therefore now the second constellation in the Zodiac. It is situated next east 
of Pisces, and is midway between the Triangles and the Fly on the N. and the head of 
Cetus on the S. It contains 66 stars, of which, one is of the 2d, one of the 3d, and two of 
the 4th magnitudes. 

" First, from the east, the Ram conducts the year ; 
Whom Ptolemy with twice nine stars adorns, 
Of which two only claim the second rank ; 
The rest, when Cynthia fills the sign, are lost." 

Aries is readily distinguished by means of two bright stars in the head, about 4* apart, 
the brightest being the most north-easterly of the two. The first, which is of the 2d 
magnitude, situated in the right horn, is called Alpha Arietis, or simply ArieUs ; the 
other, which is of the 3d magnitude, lying near the left horn, is called Sheratan, and may 
be known by another star of the 4th magnitude, in the ear, \%° S. of it, called Mesartldm, 
which is thejlrst star in this constellation. **" 

Arietis and Sheratan, are one instance out of many, where stars of more than ordinary 
brightness are seen together in pairs, as in the Twins, the Little Dog, &c, the brightest 
Itar being commonly on the east. 

* See " Precession of the Equinoxes," page 270. 

60. Constellations in this chapter? Aries 22 centuries ago? Now; and why? Hot? 
distinguished ? Arietis and Sheratan ? 



ARIES. 2$ 

51. The position of Arietis affords important facilities to 
nautical science. Difficult to comprehend as it may be, to the 
unlearned, the skilful navigator who should be lost upon an 
unknown sea, or in the midst of the Pacific ocean, could, by 
measuring the distance between Arietis and the Moon, which 
often passes near it, determine at once not only the spot he was 
in, but his true course and distance to any known meridian or 
harbor on the earth. See Part II., page 206. 

Arietis comes to the meridian about 12 minutes after Shera- 
tan, on the 5th December, near where the sun does in midsum- 
mer. Arietis, also, is nearly on the same meridian with Almaack, 
in the foot of Andromeda, 19° N. of it, and culminates only 
four minutes after it. The other stars in this constellation are 
quite small, constituting that loose cluster which we see between 
the Fly on the north, and the head of Cetus on the south. 

When Arietis is on the meridian, Andromeda and Cassiopeia 
are a little past the meridian, nearly overhead, and Perseus with 
the head of Medusa, is as far to the east of it. Taurus and 
Auriga are two or three hours lower down ; Orion appears in 
the S. E., and the Whale on the meridian, just below Aries, 
while Pegasus and the Swan are seen half-way over in the west. 

The manner in which the ancients divided the Zodiac into 12 equal parts, was both 
simple and ingenious. Having no instrument that would measure time exactly, " they 
took a vessel, with a small hole in the bottom, and having filled it with water, suffered the 
same to distill, drop by drop, into another vessel set beneath to receive it, beginning at 
the moment when some star rose, and continuing till it rose the next following night, when 
it would have performed one complete revolution in the heavens. The water falling down 
into the receiver they divided into twelve equal parts ; and having twelve other small 
vessels in readiness, each of them capable of containing one part, they again poured all 
the water into the upper vessel, and observing the rising of some star in the Zodiac, at 
the same time suffered the water to drop into one of the small vessels. And as soon as it 
was full, they removed it, and set an empty one in its place. Just as each vessel was full, 
they took notice what star of the Zodiac rose at that time, and thus continued the process 
through the year, until the 12 vessels were filled." 

Thus the Zodiac was divided into 12 equal portions, corresponding to the 12 months of 
the year, commencing at the vernal equinox. Each of these portions served as the 
visible representative or sign of the month it appeared in. 

All those stars in the Zodiac which were observed to rise while the first vessel was fill- 
ing, were constellated and included in the first sign, and called Aries, an animal held in 
great esteem by the shepherds of Chaldea. All those stars in the Zodiac which rose while 
the second vessel was filling, were constellated and included in the second sign, which, 
for a similar reason, was denominated Taurus; and all those stars which were observed 
to rise while the third vessel was filling, were constellated in the third sign, and called 
Gemini, in allusion to the twin season of the flocks. 

Thus each sign of 30° in the Zodiac, received a distinctive appellation, according to the 
fancy or superstition of the inventors ; which names have ever since been retained, 
although the constellations themselves have since left their nominal signs more than 30° 
behind. The sign Aries, therefore, included all the stars embraced in the first 30° of the 
Zodiac, and no more. The sign Taurus, in like manner, included all those stars embraced 

51. Position of Arietis ? Importance to mariners ? When come to meridian ? Where 
Andromeda and Cassiopeia then ? Perseus ? Taurus, Auriga, Orion, Pegasus and Swan ? 
What of other stars in Aries ? Ancient method of dividing the Zodiac ? Names of 
Bigns ? 



30 ASTRONOMY. 

in the next 30* of the Zodiac, or those between 30° and 60°, and so of the rest. Of those 
who imagine that the twelve constellations of the Zodiac refer to the twelve tribes of 
Israel, some ascribe Aries to the tribe of Simeon, and others, to Gad. 

HISTORY. 

According to fable, this is the ram which bore the golden fleece, and carried Phryxus 
and his sister Helle through the air, when they fled to Colchis from the persecution of their 
stepmother Ino. The rapid motion of the ram in his aerial flight high above the earth, 
caused the head of Helle to turn with giddiness, and she fell from his back into that part 
of the sea which was afterwards called Hellespont, in commemoration of the dreadful 
event. Phryxus arrived safe at Colchis, but was soon murdered by his own father-in-law, 
JEtes, who envied him his golden treasure. This gave rise to the celebrated Argonautic 
expedition under the command of Jason, for the recovery of the golden fleece. 

Nephele, Queen of Thebes, having provided her children, Phryxus and Helle, with this 
noble animal, upon which they might elude the wicked designs of those who sought their 
life, was afterwards changed into a cloud, as a reward for her parental solicitude; and 
the Greeks ever after called the clouds by her name. But the most probable account of 
the origin of this constellation is given in a preceding paragraph, where it is referred to 
the flocks of the Chaldean shepherds. 

During the campaigns of the French army in Egypt, General Dessaix discovered among 
the ruins at Dendera, near the banks of the Nile, the great temple supposed by some to 
have been dedicated to Isis, the female deity of the Egyptians, who believed that the ris- 
ing of the Nile was occasioned by the tears which she continually shed for the loss of her 
brother Osiris, who was murdered by Typhon. Others suppose this edifice was erected 
for astronomical purposes, from the circumstance that two Zodiacs were discovered, 
drawn upon the ceiling, on opposite sides. On both these Zodiacs the equinoctial points 
are in Leo, and not in Aries ; from which it has been concluded, by those who pertina- 
ciously endeavor to array the arguments of science against the chronology of the Bible 
and the validity of the Mosaic account, that these Zodiacs were constructed when the sun 
entered the sign Leo, which must have been 9T20 years ago, or 4000 years before the 
inspired account of the creation. The infidel writers in France and Germany make it 
10,000 years before. But we may " set to our seal," that whatever is true in fact and cor- 
rect in inference on this subject will be found, in the end, not only consistent with the 
Mosaic record, but with the common meaning of the expressions it uses. 

The discovery of Champollion has put this question for ever at rest ; and M. Latronne, 
a most learned antiquary, has very satisfactorily demonstrated that these Egyptian 
Zodiacs are merely the horoscopes of distinguished personages, or the precise situation 
of the heavenly bodies in the Zodiac at their nativity. The idea that such was their pur- 
pose and origin, first suggested itself to this gentleman on finding, in the box of a mummy, 
a similar Zodiac, with such inscriptions and characters as determined it to be the horo- 
scope of the deceased person. 

Of all the discoveries of the antiquary among the relics of ancient Greece, the ruins o. 
Palmyra, the gigantic pyramids of Egypt, the temples of their gods, or the sepulchres of 
their kings, scarcely one so aroused and riveted the curiosity of the learned, as did the 
discovery of ChampoUion the younger, which deciphers the hieroglyphics of ancient 
Egypt. 

The potency of this invaluable discovery has already been signally manifested in set- 
tling a formidable controversy between the champions of infidelity and those who main- 
tain the Bible account of the creation. It has been shown that the constellation Pisces, 
since the days of Hipparchus, has come, by reason of the annual precession, to occupy 
the same apparent place in the heavens that Aries did two thousand years ago. The 
Christian astronomer and the infidel are perfectly agreed as to the fact, and the amount 
of this yearly gain in the apparent motion of the stars. They both believe, and both can 
demonstrate, that the fixed stars have gone forward in the Zodiac about 50" of a degree 
in every revolution of the heavens since the creation ; so that were the world to light 
upon any authentic inscription or record of past ages, which should give the true posi- 
tion or longitude of any particular star at that time, it would be easy to fix an unques- 
tionable date to such a record. Accordingly, when the famous " Egyptian Zodiacs," 
which were sculptured on the walls of the temple at Dendera, were brought away en 
masse, and exhibited in the Louvre at Paris, they enkindled a more exciting interest in 
the thousands who saw them, than ever did the entrance of Napoleon. "Educated men 
of every order, and those who had the vanity to think themselves such," says the com- 
mentator of Champollion, " rushed to behold, the Zodiacs. These Zodiacs were imme- 
diately published and commented upon, with more or less good faith and decorum. 

History.— Discovery in Egypt? Use made of the Zodiacs? What did they prove to 
be ? How ascertained ? Who most zealous in opposing revelation ? Means employed t 



TRIADS GUL.E. 31 

Science struck out into systems very bold ; and the spirit of infidelity, seizing upon the 
discovery, flattered itself with the hope of drawing from thence new support. It was 
unjustifiably taken for granted, that the ruins of Egypt furnished astronomy with monu- 
ments, containing observations that exhibited the state of the heavens in the most 
remote periods. Starting with this assumption, a pretence was made of demonstrating 
by means of calculations received as infallible, that the celestial appearances assigned 
to these monuments extended back from forty-five to sixty-five centuries ; that the 
Zodiacal system to which they must belong, dated back fifteen thousand years, and must 
reach far beyond the limits assigned by Moses to the existence of the world." Among 
those who stood forth more or less bold as the adversaries of Revelation, the most pro- 
minent was M. Dupuis, the famous author of L 'origine de tons les Oultes. 

The infidelity of Dupuis was spread about by means of pamphlets, and the advocates 
of the Mosaic account were scandalized " until a new Alexander arose to cut the Gordian 
knot, which men had vainly sought to untie. This was Champollion the younger, armed 
with his discovery." The hieroglyphics now speak a language that all can understand, 
and no one gainsay. " The Egyptian Zodiacs, then," says Latronne, " relate in no respect 
to astronomy, but to the idle phantasies of judicial astrology, as connected with the des- 
tinies of the emperors who made or completed them." 

TELESCOPIC OBJECTS. 

1. a Arietis — A double star in the Ram's forehead ; R. A. lh. 58m. 10s ; Dec. N. 22° 
42' 02°. A3, yellow; B 11, purple. 

Two thousand years ago the first meridian or Vernal Equinox passed through this 
star; but the recession of the equinox at the slow rate of 50" per year, has, in that length 
of time, carried the equinoctial nearly 60° to the west, where we now find it. See this 
subject explained in the second part of the book. 

2. j3 Arietis (Sheratan) — A bright star with a distant companion in the coil of the 
right horn ; R. A. lh. 45m. 49s. ; Dec. N. 20° 01' 04". A 3, pearly white ; B 11, dusky. 

3. y Arietis ( Mesarthim) — a double star just south of /? ; R. A. lh. 44m. 45s. ; Dec. N. 
18° 30' 05". A 4>£, bright white ; B 5, pale grey. A fine object. Map VIII., Fig. 2- 

4. £ Arietis — A very close double star near the root of the tail, and between it and 
Musca; R. A. 2h. 50m. 04s.; Dec. N. 20° 41' 08". A 5, pale yellow; B 6%, whitish. It 
requires a good telescope to separate them. 

5. 71" Arietis — A neat triple star in the haunch, about one-third of the distance from 
[3 Arietis to Aldebaran; R. A. 2h. 40m. 22s.; Dec. N. 16° 47' 08". A 5, pale yellow; B 
83*2, flushed ; C 11, dusky. A beautiful trio. 

6. A quadruple star half way between a and y under the right horn ; R. A. lh. 50m. 
43s.; Dec. N. 20° 16' 07". A 6, topaz yellow; B 15, deep blue; C 10, lilac; D, pale blue. 
An exquisite object. 

7. A round nebula near y Arietis, and just east of it; R. A. lh. 50m. 34s. ; Dec. N 
18° 13' 06". It is large and pale, and lies among some small stars, some of which form a 
curve across the south part of the field. 



TRIANGULA (the triangles).— MAP II. 

52. The Triangles are situated between the head of Aries on 
the north, and the feet of Andromeda on the south. R. A. 
2h. ; Dec. IN". 30°. They contain two stars of the 4th magni- 
tude, and two of the 5th ; with several smaller. A line from 
Sheratan in Aries, to Almaack, will pass through the lucida 
Trianguli, about midway between them. 

Telescopic Objects? What a Arietis? Other double stars? Triple? Quadruple? 
Any clusters ? Nebulae ? 
52. Situation of the Triangles ? Number and size of stars ? How find their lucida? 



32 ASTRONOMY. 

HISTORY. 

The upper or Northern Triangle is one of the ancient 48 asterisms; and Hevelius took 
three other stars between it and the head of Aries, to form TriangvJ/wm minus. The 
latter figure, however, is discontinued, though shown on the map. 

TELESCOPIC OBJECTS. 

1 a Trianguli — A bright fourth magnitude star, with a Telescopic companion ; R. A. 
lh. 43m. 5Ss. ; De«. N. 28° 47' 08". A 3%, yellow ; B 11, lilac. 

2. e Trianguli — A most delicate double star ; R. A. lh. 53m. 38s. : Dec. N. 32° 30' 05". 
A 5%, bright yellow ; B 15, dusky. 

3. A large and distinct but faint pale white nebula, between the Triangles and the 
head of the Northern Fish; R. A. lh. 24m. 51s.; Dec. N. 29° 51' 03". A bright star a 
little north-west, and five others more remote in the east. 



MUSOA (the fly).— MAP II. 

53. This very small constellation lies directly between the 
back of Aries on the south, and the head of Medusa on the 
north. It has one star of the 2d, two of the 4th, and two of 
the 5th magnitudes. An unimportant asterism, and not always 
mentioned in the catalogues, though shown on the map. 

TELESCOPIC OBJECTS. 

1. A fine double star over the back of Aries, nearly midway between the Pleiades and 
/3 Andromedse ; R. A. 2h. 31m. 20s. ; Dec. N. 2G° 22' 02". A 6, pale topaz ; B 9, light blue. 
An easy object. 

2. a Muscle — a coarse quadruple star, in the body of the figure, and forming its 
lucida ; R. A. 2h. 40m. 34s. ; Dec. N. 26° 35' 09". A 3, white ; B 13, deep blue ; C 11, lurid ; 
D 9, pale grey. Both these objects are usually classed as belonging to Aries. 



OETUS (THE WHALE).— MAP II. 

54. As the whale is the chief monster of the deep, and the 
largest of the aquatic race, so is it the largest constellation in 
the heavens. It occupies a space of 50° in length, E. and W., 
with a mean breadth of 20° from N. to S. It is situated below 
Aries and the Triangles, with a mean declination of 12° S. It 
is represented as making its way to the E., with its body below, 
and its head elevated above the equinoctial ; and is six weeks in 
passing the meridian. Its tail comes to the meridian on the 10th 
of November, and its head leaves it on the 22d of December. 

55. This constellation contains 91 stars ; two of the 2d mag- 
nitude, ten of the 3d, and nine of the 4th. The head of Cetus 



History. — Which ancient? Who formed the other? Now recognized, or not? 

Telescopic Objects? Double stars ? Nebulas? 

53. Situation of Musca ? Stars ? Relative importance ? Is it always recognized as a 
constellation? 54. Cetus? Comparative size? Situation? How represented? 

55. Number of stars 9 Magnitudes ? How may the head of Cetus be known ? Brightest 



CETUS. 33 

may be readily distinguished, about 20° S. B.of Aries, by means 
of five remarkable stars, 4° and 5° apart, and so situated as to 
form a regular pentagon. The brightest of these is Menkar, of 
the 2d magnitude, in the nose of the Whale. It occupies the 
S. E. angle of the figure. It is 3^° N. of the equinoctial, and 
15° E. of El Rischa in the bight of the cord between the Two 
Fishes. It is directly 37° S. of Algol, and nearly in the same 
direction from the Fly. It makes an equilateral triangle with 
Arietis and the Pleiades, being distant from each about 23° S., 
and may otherwise be known by a star of the 3d magnitude in 
the mouth, 3° W. of it, called Gamma, placed in the south mid- 
dle angle of the pentagon. 

56. Nw is a star of the 4th magnitude, 4° N. W. of Gamma, 
and these two constitute the S. W. side of the pentagon in the 
head of the Whale, and the N. E. side of a similar oblong figure 
in the neck. 

Three degrees S. S. W. of Gamma, is another star of the 3d 
magnitude in the lower jaw, marked Delta, constituting the E. 
side of the oblong pentagon ; and 6° S. W. of this, is a noted 
star in the neck of the Whale, called Mir a, or the " wonderful 
star of 1596," which forms the S. E. side. This variable star 
was first noticed as such by Fabricius, on the 13th of August, 
1596. It changes from a star of the 2d magnitude so as to 
become invisible once in 234 clays, or about 7 times in 6 years. 
Herschel makes its period 331 clays, 10 hours, and 19 minutes ; 
while Hevelius assures us that it once disappeared for 4 years ; 
so that its true period, perhaps, has not been satisfactorily deter- 
mined. 

The whole number of stars ascertained to be variable amounts to only 15 ; while those 
which are suspected to be variable, amount to 37. 

57. Mir a is 7° S. S. E. of El Rischa, in the bend or knot of 
the ribbon which connects the Two Fishes. Ten degrees S. of 
Mira, are 4 small stars, in the breast and paws, about 3° apart, 
which form a square, the brightest being on the E. Ten degrees 
S. W. of Mira is a star of the 3d magnitude, in the heart, 
called Baten Kaitos, which makes a scalene triangle with two 
other stars of the same magnitude 7° and 10° W. of it ; also, 
an equilateral triangle with Mira and the easternmost one in 
the square. 

Btar ? Position ? Name ? 56. Size and Position of Nu ? Delta ? Mira ? Position ? 
Peculiarity? When, and by whom first noticed? Period and extent of variability? 
Whole number of variable stars? 57. Baten Kaitos? Position with regard to Mira = 
To other stars ? 



34 ASTRONOMY. 



A great number of geometrical figures may be formed from the stars in this, and In 
most of the other constellations, merely by reference to the maps ; but it is better that 
the student should exercise his own ingenuity in this way with reference to the stars 
themselves, for when once he has constructed a group into any letter or figure of his own 
invention, he never will forget it. 

The teacher should therefore require his class to commit to writing the result of their 
own observations upon the relative position, magnitude and figures of the principal stars 
in each constellation. One evening's exercise in this way will disclose to the student a 
surprising multitude of crosses, squares, triangles, arcs and letters, by which he will be 
better able to identify and remember them, than by any instructions that could be given. 

For example : Mira and Baten in the Whale, about 10° apart, make up the S. E. or 
shorter side of an irregular square, with El Bischa in the node of the ribbon, and another 
star in the Whale as far to the right of Baten, as El Bischa is above Mira. Again, 

There are three stars of equal magnitude, forming a straight line W. of Baten ; from 
which, to the middle star is 10°, thence to the W. one 12 J^ ; and 8° or 9° S. of this line, 
in a triangular direction, is a bright star of the second magnitude in the coil of the tail, 
called Diphda. 

In a southerly direction, 25° below Diphda, is Alpha in the head of the Phenix, and 
about the same distance S. W. is Fomalhaut, in the mouth of the Southern Eish, forming 
together a large triangle, with Diphda in the vertex or top of it. 

That fine cluster of small stars S. of the* little square in the Whale, constitutes a part 
of a new constellation called the Chymical Furnace. The two stars N. E., and the 
three to the southward of the little square, are in the river Eridawus. 

HISTORY. 

This constellation is of very early antiquity: though most writers consider it the 
famous sea-monster sent by Neptune to devour Andromeda because her mother Cassio- 
peia had boasted herself fairer than Juno or the Sea Nymphs ; but slain by Perseus and 
placed among the stars in honor of his achievement. 

" The winged hero now descends, now soars, 
And at his pleasure the vast monster gores. 
Deep in his back, swift stooping from above, 
His crooked sabre to the hilt he drove." 

It is quite certain, however, that this constellation had a place in the heavens long 
prior to the time of Perseus. When the equinoctial sun in Aries, which is right over the 
head of Cetus, opened the year, it was denominated the Preserver, or Deliverer, by the 
idolaters of the East. On this account, according to Pausanius, the sun was worshipped, 
at Eleusis, under the name of the Preserver or Saviour. 

" With gills pulmonic breathes the enormous whale, 
And spouts aquatic columns to the gale ; 
Sports on the shining wave at noontide hours, 
And shifting rainbows crest the rising showers." — Darwin. 

TELESCOPIC OBJECTS. 

1. (3 Ceti— A double star ; R. A. Oh. 35m. 34s. ; Dec. S. 18° 51' 9'. A 2%, yellow ; B 12, 
pale blue. 

2. y Ceti — A close double star in the Whale's mouth ; R. A. 2h. 35m. 01s. ; Dec. N. 
2° 33' 5". A 3, pale yellow ; B 7, lucid blue ; the colors finely contrasted. 

3. v A double star in the Whale's eye ; y R. A. 2h. 27m. 29s. ; Dec. N. 4° 53' 5". A 4j£, 
pale yellow ; B 15, blue. 

4. A long narrow nebula, of a pale, milky tint ; R. A. Oh. 39m. 45s. ; Dec. S. 26° 
10' V. It is situated in the space south of the tail of Cetus, near a line drawn from 
a Andromeda to /3 Ceti. Discovered by Miss Herschel, in 1783. 

5. A planetary nebula; R. A. 2h. 19m. 25s.; Dec. S. 1° 51' 6"; in the middle of the 
Whale's neck. 

6. A bright round nebula ; R. A. lh. 23m. 20s. ; Dec. S. 7° 41' 8". Registered by Sh' 
W. Herschel, 1785. It is just above the Whale's back. 

History. — Antiquity? Its original name ? When, and why? What worship in con- 
sequence ? 
Telescopic Objects.— Beta ? Gamma? Nu? Nebulse? 



PERSEUS, ET CAPUT MEDUSAE. 35 

7. A round stellar nebula, near 6 in the Whale's lower jaw, and about 2%° from J- 
on a line towards € , or south by west. A very distant object, classed by Sir W. Herschel, 
as 910 times as distant as stars of the first magnitude. 



PERSEUS, ET CAPUT MEDUSAE.— MAP III. AND IV. 

58. Perseus is represented with a sword in his right hand, 
the head of Medusa in his left, and wings at his feet. It is 
situated directly IS", of the Pleiades and the Fly, between 
Andromeda on the W. and Auriga on the E. Its mean decli- 
nation is 46° N. It is on the meridian the 24th of December. 
It contains, including the head of Medusa, 59 stars, two of 
which are of the 2d magnitude, and four of the 3d. According 
to Eudosia, it contains, including the head of Medusa, 6t stars. 

; Perseus next, 



Brandishes high in heaven his sword of flame, 
And holds triumphant the dire Gorgon's head, 
Flashing with fiery snakes ! the stars he counts 
Are sixty-seven ; and two of these he boasts, 
Nobly refulgent in the second rank — 
One in his vest, one in Medusa's head." 

09. The Head of Medusa is not a separate constellation, 
but forms a part of Perseus. It is represented as the trunkless 
head of a frightful Gorgon, crowned with coiling snakes, instead 
of hair, which the victor Perseus holds in his hand. There are, 
in all, about a dozen stars in the head of Medusa ; three of the 
4th magnitude, and one, varying alternately from the 2d to the 
4th magnitude. This remarkable star is called Algol. It is 
situated 12° E. of Almaack, in the foot of Andromeda, and may 
be known by means of three stars of the 4th magnitude, lying a 
few degrees S. W. of it, and forming a small triangle. It is on 
the meridian the 21st of December ; but as it continues above 
the horizon 18 hours out of 24, it may be seen every evening 
from September to May. It varies from the 2d to the 4th 
magnitude in about 3|- hours, and back again in the same time ; 
after which it remains steadily brilliant for 2f days, when the 
same changes recur. 

The periodical variation of Algol was determined in 1783, by John Goodricke, of York 
(Eng.), to be 2 days, 20 hours, 43 minutes, and 56 seconds. Dr. Herschel attributes the 
variable appearance of Algol to spots upon its surface, and thinks it has a motion on its 
axis similar to that of the sv/n. He also observes, of variable stars generally : — " The 
rotary motion of the stars upon their axis is a capital feature in their resemblance to 
the sun. It appears to me now, that we cannot refuse to admit such a motion, and that 
indeed it may be as evidently proved as the diurnal motion of the earth. Dark spots, 



58. Perseus? How represented ? When on the meridian? Number of stars? Size? 
59. Head of Medusa? How represented? Number of stars? What remarkable one? 
Situation? Variableness and period? When and by whom determined? Supposed 
cause of variability?* Lalande? 

2* 



36 ASTRONOMY. 

or large portions of the surface less luminous than the rest, turned alternately in certain 
directions either toward, or from us, will account for all the phenomena of periodical 
changes in the lustre of the stars, so satisfactorily, that we certainly need not look out 
for any other cause." 

It is said that the famous astronomer Lalande, who died at Paris in 1807, was wont to 
remain whole nights, in his old age, upon the Pont Neuf, to exhibit to the curious the 
variations in the brilliancy of the star Algol. 

60. Nine degrees E. by N. from Algol, is the bright star Alge- 
nib, of the 2d magnitude, in the side of Perseus, which with Al- 
maack, makes a perfect right angle at Algol, with the open part 
towards Cassiopeia. By means of this strikingly perfect figure, 
the three stars last mentioned may always be recognized without 
the possibility of mistaking them. Algenib may otherwise be 
readily distinguished by its being the brightest and middle one 
of a number of stars lying four and five degrees apart, in a large 
semicircular form, curving towards Ursa Major. 

Algenib comes to the meridian on the 21st December, 15 minutes after Algol, at which 
time the latter is almost directly overhead. When these two stars are on the meridian, 
that beautiful cluster, the Pleiades, is about half an hour E. of it; and in short, the 
most brilliant portion of the starry heavens is then visible in the eastern hemisphere. 
The glories of the scene are unspeakably magnificent; and the student who fixes his 
eye upon those lofty mansions of being, cannot fail to covet a knowledge of their order 
and relations, and to "reverence Him who made the Seven Stars and Orion." 

61. The Milky Way around Perseus is very vivid, being undoubt- 
edly a rich stratum of fixed stars, presenting the most wonder- 
ful and sublime phenomenon of the Creator's power and great- 
ness. Kohler, the astronomer, observed a beautiful nebula near 
the face of Perseus, besides eight other nebulous clusters in dif- 
ferent parts of the constellation. 

The head and sword of Perseus are exhibited on the circumpolar map. That very 
bright star 23° E. of Algol, is Capella in the Charioteer. 

HISTORY 

Perseus was the son of Jupiter and Danae. He was no sooner born than he was cast 
into the sea, with his mother ; but being driven on the coasts of one of the islands of the 
Cyclades, they were rescued by a fisherman, and carried to Polydectes, the king of the 
place, who treated them with great humanity, and intrusted them to the care of the 
priests of Minerva's temple. His rising genius and manly courage soon made him a 
favorite of the gods. At a great feast of Polydectes, all the nobles were expected to 
present the king with a superb and beautiful horse ; but Perseus, who owed his benefac- 
tor much, not wishing to be thought less munificent than the rest, engaged to bring him 
the head of Medusa, the only one of the three Gorgons, who was subject to mortality. 
The names of the other two were Stheno and Euryale. They were represented with ser- 
pents wreathing round their heads instead of hair, having yellow wings and brazen 
hands ; their bodies which grew indissolubly together, were covered with impenetrable 
scales, and their very looks had the power of turning into stones all those on whom 
they fixed their eyes. 

To equip Perseus for this perilous enterprise, Pluto, the god of the infernal regions, 
lent him his helmet, which had the power of rendering the wearer invisible. Minerva, 
the goddess of wisdom, furnished him with her buckler, which was as resplendent as a 
polished mirror ; and he received from Mercury wings for his feet, and a dagger made 



60. Algenib? How known? When on the meridian ? Where, then, are the Pleiades? 
What the general aspect of the heavens? 61. Milky Way around Perseus? Observa- 
tion of Kohler? 

Histoky. — Who was Perseus? What fate at birth, &c. ? 



PERSEUS, ET CAPUT MEDUSA. 3*7 

of diamonds. Thus equipped, he mounted into the air, conducted by Minerva, and came 
upon the monsters who, with the watchful snakes about their heads, were all asleep. He 
approached them, and with a courage which amazed and delighted Minerva, cut off with 
one blow Medusa's head. The noise awoke the two immortal sisters, but Pluto's helmet 
rendered Perseus invisible, and the vengeful pursuit of the Gorgons proved fruitless. 
" In the mirror of his polished shield 
Reflected, saw Medusa slumbers take, 
And not one serpent by good chance awake; 
Then backward an unerring blow he sped, 
And from her body lopped at once her head." 
Terseus then made his way through the air, with Medusa's head yet reeking in his 
hand, and from the blood which dropped from it as he flew, sprang all those innumerable 
serpents that have ever since infested the sandy deserts of Libya. 
" The victor Perseus, with the Gorgon head, 
O'er Libyan sands his airy journey sped, 
The gory drops distilled, as swift he flew, 
And from each drop envenomed serpents grew." 

The destruction of Medusa rendered the name of Perseus immortal, and he was 
changed into a constellation at his death, and placed among the stars, with the head of 
Medusa by his side, 

TELESCOPIC OBJECTS. 

1. a Perset — A fine double star; R. A. 3h. 12m. 55s. : Dec. N. 49° 17' 2". A 2%, bril- 
liant lilac ; B 9, cinereous. This is JIgenib, in the hero's left side. 

2. ft Persei, or Algol ; R. A. 2h. 57m. 46s. ; Dec. N. 41° 20'. A variable double star. 
A 2 to 4, whitish ; B 11, purple. The former varies in brightness periodically, from the 
2d to the 4th magnitude, and back again to the 2d magnitude, period being 2d. 20h. 4Sm. 
56s. ; an object of great interest. 

3. y Persei— A wide unequal double star in the hero's left shoulder ; R. A. 2h. 53m. 
14s. ; Dec. N. 52° 52' 4'. A 4, flushed white ; B 14, clear blue. 

4. 6 Persei — A bright star with a companion in the hero's hip; R. A., 3h. 31m. 33s.; 
Dec, N. 47° 16' 2". About 3° south-west of a Persei. A 3%, white ; B 11, pale blue. 

5. e Persei — A neat double star in the right knee ; R. A. 3h. 47m. 08s. ; Dec. N. 39* 
32' 4". A 3%, pale white ; B 9, lilac ; a fine delicate object. 

6. £ Persei — A delicate quadruple star ; R. A. 3h. 44m. 05s. ; Dec. N. 31° 24' 2". 
A 3%, flushed white; BIO, smalt blue; C 12, ash-colored; D 11, blue. It is situated in 
the right foot, and is designated by Smyth as " an elegant group." 

7. v Persei— A fine double star in the head of the figure ; R. A. 2h. 39m. 04s. ; Dec. 
N. 55" 13' 5". A 5, orange ; B 8}£, smalt blue ; the colors in fine contrast. 

8. A gorgeous cluster in the sword handle of Perseus ; R. A. 2h. 08m. 58s. ; Dec. N. 
56° 24' 4". It may be seen with the naked eye, and when seen through a good telescope, 
is one of the most magnificent objects in the heavens. Map VLU., Fig. 25. 

9. An extensive and rich cluster on the right side of Perseus, in a rich portion of 
the galaxy. R. A. 3h. 04m. 01s.; Dec. N. 46° 37' 9". Smyth says "it has a gathering 
spot about 4' in diameter, where the star-dust glows among minute points of fight." 
Herschel says, " the large stars are arranged in lines like interwoven letters. 

10. An elongated nebula; R. A. 2h. 30m. 25s.; Deo. N. 38° 21' 3" ; supposed to be a 
vast ring, seen obliquely. Map VIII., Fig. 26. 

11. A pretty compressed oval group of stars, in the left knee of Perseus, nearly mid- 
way between "A and fl; R. A. 3h. 58m. lis. ; Dec. N. 49° 04' 05". A well-marked object, 
surrounded by a curve of larger stars, somewhat in the form of the letter D. Map VHT., 
Fig. 27. 

Telescopic Objects.— Alpha? Beta? Gamma? Delta? Epsilon? Zeta? Eta? 
Clusters ? Nebula? Which shown on the map? 



38 ASTRONOMY. 

CHAPTER III. 

CONSTELLATIONS ON THE MERIDIAN IN JANUARY. 

TAITBUS (the bull).— MAP III. 

62. Taurus is represented in an attitude of rage, as if about 
to plunge at Orion, who seems to invite the onset by provoca- 
tions of assault and defiance. Only the head and shoulders of 
the animal are to be seen ; but these are so distinctly marked 
that they cannot be mistaken. 

The constellations which pass our meridian in the months of January, February and 
March, present to us the most brilliant and interesting portion of the heavens ; embrac- 
ing an annual number of stars of the highest order and brightness, all so conspicuously 
situated, that the most inexperienced can easily trace them out. 

63. Taurus is now the second sign and third constellation of the 
Zodiac ; but anterior to the time of Abraham, or more than 
4000 years ago, the vernal equinox took place, and the year 
opened when the sun was in Taurus; and the Bull, for the space 
of 2000 years, was the prince and leader of the celestial host. 
The Ram succeeded next, and now the Pishes lead the year. 
The head of Taurus sets with the sun about the last of May, 
when the opposite constellation, the Scorpion, is seen to rise in 
the S. E. It is situated between Perseus and Auriga on the 
north, Gemini on the east, Orion and Eridanus on the south, and 
Aries on the west, having a mean declination of 16° N. 

64. Taurus contains 141 visible stars, including two remark- 
able clusters called the Pleiades and Hyades. The first is now 
on the shoulder, and the latter in the face of the Bull. The 
names of the Pleiades are Alcione, Merope, Maia, Electra, 
Tayeta, Sterope and Celeno. Merope was the only one who 
married a mortal, and on that account her star is dim among her 
sisters. Although but six of these are visible to the naked eye, 
yet Dr. Hook informs us that, with a twelve feet telescope, he 
saw 18 stars; and Rheita affirms that he counted 200 stars in 
this small cluster. For its appearance through an ordinary tele- 
scope, see Map VIIL, Fig. 28. 

The most ancient authors, such as Homer, Attalus, and Geminus, counted only sice 
Pleiades; but Simonides, Varro, Pliny, Aratus, Hipparchus, and Ptolemy, reckon them 

62. How is Taurus represented? How much of him seen? What constellations most 
brilliant? 63. In what sign is Taurus ? What constellation? How 4000 years ago? 
What next led the year? What now? At what time does Taurus set with the sun? 
How situated? 64. How many visible stars in Taurus? Clusters? How situated? 
Names of the Pleiades? What said of Merope? How many of the Pleiades visible to 
the naked eye? Dr. Hook and Rheita? Ancient authors? 



TAURUS. 39 

seven in number; and it was asserted, that the seventh had been seen before the burn- 
ing of Troy; but this difference might arise from the difference in distinguishing them 
with the naked eye. 

65. The Pleiades are so called from the Greek word, ttXeelv 
pleein, to sail; because at this season of the year, they were 
considered "the star of the ocean" to the benighted mariner. 

Virgil who flourished 1200 years before the invention of the magnetic needle, says 
that the stars were relied upon, in the first ages of nautical enterprise, to guide the rude 
bark over the seas. 

"Tunc alnos primum fiuvii sensere cavatas ; 
Navita turn stellis numeros, et nomina fecit, 
Pleiadas, Hyadas, claramque Lycaonis Arcton." 
" Then first on seas the shallow alder swam ; 
Then sailors quarter'd heaven, and found a name 
For every fix'd and every wand'ring star — 
The Pleiades, Hyades, and the Northern Car." 
The same poet also describes Palinurus, the renowned pilot of the Trojan fleet, as 
watching the face of the nocturnal heavens. 

"Sidera cuncta notat tacito iabentia coelo, 
Arcturum, pluviasque Hyadas, geminosque Triones, 
Armatumque auro circumspicit Oriona." 
" Observe the stars, and notes their sliding course, 
The Pleiades, Hyades, and their wat'ry force ; 
And both the Bears is careful to behold, 
And bright Orion, arm'd with burnished gold." 

Indeed, this sagacious pilot was once so intent in gazing upon the stars while at the 
helm, that he fell overboard, and was lost to his companions. 

" Headlong he fell, and struggling in the main, 
Cried out for helping hands, but cried in vain." 

66. Alcyone, of the 3d magnitude, being the brightest star in 
this cluster, is sometimes called the light of the Pleiades. The 
other five are principally of the 4th and 5th magnitudes. The 
Pleiades, or, as they are more familiarly termed, the seven stars, 
come to the meridian 10 minutes before 9 o'clock, on the even- 
ing of the 1st of January, and may serve in place of the sun, to 
indicate the time, and as a guide to the surrounding stars. 

According to Hesiod, who wrote about 900 years before the birth of our Savior, tht 
heliacal rising of the Pleiades took place on the 11th of May, about the time of harvest. 
" When, Atlas-born, the Pleiad stars arise 
Before the sun above the dawning skies, 
'Tis time to reap ; and when they sink below 
The morn-illumined west, 'tis time to sow." 

Thus, in all ages, have the stars been observed by the husbandman, for " signs and 
for seasons." 

Pliny says that Thales, the Miletan astronomer, determined the cosmical setting of 
the Pleiades to be 25 days after the autumnal equinox. This would make a difference 
between the setting at that time and the present, of 35 days, and as a day answers to 
about 59' of the ecliptic, these days will make 34° 25'. This divided by the annual pre- 
cession (50%"), wm g ive 2465 years since the time of Thales. Thus does astronomy 
become the parent of chronology. 



65. Why Pleiades so called? Remark, and quotations from Virgil? 66. What said 
of Alcyone ? Of the other five ? When on the meridian ? Serve what purpose ? Period, 
and remark of Hesiod? Of Pliny? What calculation respecting the passage of the 
Pleiades over the meridian ? 



40 ASTRONOMY. 

If it be borne in mind that the stars uniformly rise, come to the meridian, and set about 
four minutes earlier every succeeding night, it will be very easy to determine at what 
time the seven stars pass the meridian on any night subsequent or antecedent to the 
1st of January. For example : at what time will the seven stars culminate on the 5th 
of January ? Multiply the 5 days by 4, and take the result from the. time they culminate 
on the 1st, and it will give 30 minutes after 8 o'clock in the evening. 

67. The Pleiades are also sometimes called Vergilia, or the 
" Yirgins of Spring ;" because the sun enters this cluster in the 
" season of blossoms," about the 18th or May. He who made 
them alludes to this circumstance when he demands of Job : 
" Canst thou bind the sweet influences of the Pleiades," &c. — 
(Job 38 : 31.) 

The Syrian name of the Pleiades is Suecoth, or Suceoth-Benoth, derived from a Chal- 
daic word, which signifies " to speculate, to observe," and the " Men of Suecoth" 
(2 Kings IT : 30) have been thence considered observers of the stars. 

68. The Hyades are situated 11° S. E. of the Pleiades, in the 
face of the Bull, and may be readily distinguished by means of 
fiye stars so placed as to form the letter Y. (Map YIIL, Fig. 
29.) The most brilliant star is on the left, in the top of the 
letter, and called Aldebaran ; from which the moon's distance is 
computed. 

" A star of the first magnitude illumes 
His radiant head ; and of the second rank, 
Another beams not far remote." 

The ancient Greeks counted seven in this cluster : — 

" The Bull's head shines with seven refulgent flames, 
Which, Grecia, Hyades, from their showering names." 

69. Aldebaran is of Arabic origin, and takes its name from 
two words which signify, " He went before, or led the way" — 
alluding to that period in the history of astronomy when this 
star led up the starry host from the vernal equinox. It comes 
to the meridian at 9 o'clock on the 10th of January, or 48-J- 
minutes after Alcyone, on the 1st. When Aries is about 21° 
high, Aldebaran is just rising to the east. So Manilius : — 

" Thus, when the Bam hath doubled ten degrees, 
And join'd seven more, then rise the Hyades." 
A line 15%° E. N. E. of Aldebaran will point out a bright star of the 2d magnitude in 
the extremity of the northern horn, marked Beta or El Nath ; (this star is also in the 
foot of Auriga, and is common to both constellations.) From Beta in the northern horn, 
to Zeta, in the tip of the southern horn, it is 8°, in a southerly direction. This star 
forms a right angle with Aldebaran and Beta. Beta and Zeta, then, in the button of the 
horns, are in a line nearly north and south, 8° apart, with the brightest on the north. 
That very bright star 173*6° N. of Beta, is Capella, in the constellation Auriga. 

67. What other name have the Pleiades, and why ? CitatioD from Job ? Syrian name ? 
68. Where are the Hyades situated ? How known ? Where the most brilliant star ? 
Name ? Are they shown on the map ? 69. Origin and import of the name Aldebaran ? 
When does it come to the meridian at 9 o'clock p.m. ? Where is Beta ? In what other 
constellation ? Zeta, and its distance? How situated with reference to Aldebaran and 
Beta? How Beta and Zeta? Capella? 



ORION. 41 

, HISTORY. 

According to the Grecian mythology, this is the animal which bore Europa over the 
seas to that country which derived from her its name. She was the daughter of Agenor, 
and princess of Phoenicia. She was so beautiful that Jupiter became enamoured of her ; 
and assuming the shape of a snow-white bull, he mingled with the herds of Agenor, 
while Europa, with her female attendants, were gathering flowers in the meadows. 
Europa caressed the beautiful animal, and at last had the courage to sit upon his back. 
The god now took advantage of her situation, and with precipitate steps retired towards 
the shore, and crossed the sea with Europa upon his back, and arrived safe in Crete. 
Some suppose she lived about 1552 years before the Christian Era. It is probable, however, 
that this constellation had a place in the Zodiac before the Greeks began to cultivate a 
knowledge of the stars ; and that it was rather an invention of the Egyptians or Chal- 
deans. Both the Egyptians and Persians worshipped a deity under this figure, by the 
name of Apis ; and Belzoni is said to have found an embalmed bull in one of the notable 
sepulchres near Thebes. 

In the Hebrew Zodiac, Taurus is ascribed to Joseph. 

The Pleiades, according to fable, were the seven daughters of Atlas and the nymph 
Pleione, who were turned into stars, with their sisters the Hyades, on account of their 
amiable virtues and mutual affection. 

Thus we everywhere find that the ancients, with all their barbarism and idolatry, 
entertained the belief that unblemished virtue and a meritorious life would meet their 
reward in the sky. Thus Virgil represents Magnus Apollo as bending from the sky to 
address the youth lulus : — ■ 

"Macte nova virtute puer; sic itur ad astra; 
Diis genite, et geniture Deos." 

" Go on, spotless boy, in the paths of virtue ; it is the way to the stars ; offspring of 
the gods thyself — so shalt thou become the father of gods." 

Our disgust at their superstitions may be in some measure mitigated, by seriously 
reflecting, that had some of these personages lived in our day, they had been orna- 
ments in the Christian Church, and models of social virtue. 

TELESCOPIC OBJECTS. 

1. a Tauei (Aldeoarari) — A star of the first magnitude with a telescopic companion ; 
R. A. 4h. 26m. 44s. ; Dec. N. 16° 10' 9". A 1, pale rose tint ; B 12, sky blue. 

2. (3Tavri(ZJI ATath)—R. A. 5h. 16m. lis.; Dec. N. 2S° 28'. A fine star, with a 
distant companion. A 2, brilliant white ; B 10, pale grey. 

3. y Tauri— One of the Hyades ; R. A. 4h. 10m. 41s. ; Dec. 11° 14' 1". A bright star, 
with a distant telescopic companion ; A 3%, yellow ; B 11, pale blue. 

4. 7] Tauri {Alcyone)— One of the Pleiades ; R. A. 8h. 37m. 57s. ; Dec. N. 23° 36' 3". 
A 3, greenish yellow; B, pale white and distant. 

5. A nebulous star; R. A. 3h. 59m. 06s.; Dec. N. 30° 20' 5". A star of the eighth 
magnitude, with a faint luminous atmosphere surrounding it, and about 3' in diameter. 
This star and nebula led Sir William Herschel to adopt his Nebula Theory, or theory of 
condensation of gas or nebulous matter, into suns and worlds. 

6. A large nebula ; R. A. 5h. 24m. 51s. ; Dec. N. 21° 54' 2". It is about one degree 
north-west of fin the tip of the Bull's southern horn. It is an oval form, with several 
minute telescopic stars in its vicinity. For drawing, see Map VHL, Fig 30. 

Of the Pleiades and Hyades, two prominent clusters, we have spoken at 64, 65. 



ORION".— MAP III. 

70. Whoever looks up to this constellation and learns its 
name, will never forget it. It is too beautifully splendid to need 
a description. When it is on the meridian, there is then above 

History.— Story of Europa and Jupiter? What probability? What said of the 
Egyptians and Persians? Hebrew zodiacs? Fabulous paternity of the Pleiades? Why 
turned into stars? What remarks respecting the ancients? 

Telescopic Objects. — Alpha? Beta? Gamma? Eta? Nebulae? Point out on the 
map. 

70. What is said of Orion? Of the view when on the meridian? How is Orion repre- 



42 ASTRONOMY. 

the horizon the most magnificent view of the celestial bodies 
that the starry firmament affords ; and it is visible to all the 
habitable world, because the equinoctial passes through the 
middle of the constellation. It is represented on celestial maps 
by the figure of a man in the attitude of assaulting the Bull, 
with a sword in his belt, a huge club in his right hand, and the 
skin of a lion in his left, to serve for a shield. 

Manilius, a Latin poet, who composed five books on astronomy a short time before the 
birth of our Saviour, thus describes its appearance : — 

" First next the Twins, see great Orion rise, 
His arms extended stretch o'er half the skies ; 
His stride as large, and with a steady pace 
He marches on, and measures a vast space ; 
On each broad shoulder a bright star display'd, 
And three obliquely grace his hanging blade. 
In his vast head, immers'd in boundless spheres, 
Three stars, less bright, but yet as great, he bears, 
But farther off removed, their splendor's lost ; 
Thus graced and arni'd he leads the starry host." 

71. The centre of the constellation is midway between the 
poles of the heavens and directly over the equator. It is also 
about 8° W. of the solstitial colure, and comes to the meridian 
about the 23d of January. The whole number of visible stars 
in this constellation is 78 ; of which, two are of the first magni- 
tude, four of the 2d, three of the 3d, and fifteen of the 4th. 

72. Those four brilliant stars in the form of a long square or 
parallelogram, intersected in the middle by the " Three Stars," 
or " Ell and Yard," about 25° S. of the Bull's horns, form the 
outlines of Orion. The two upper stars in the parallelogram are 
about 15° N. of the two lower ones ; and, being placed on each 
shoulder, may be called the epaulets of Orion. The brightest 
of the two lower ones is in the left foot, on the W., and the 
other which is the least brilliant of the four, in the right knee. 
To be more particular ; Bellatrix is a star of the 2d magnitude 
on the W. shoulder ; Betelguese is a star of the 1st magnitude, 
7-J-° E. of Bellatrix, on the E. shoulder. It is brighter than 
Bellatrix, and lies a little farther toward the north ; and comes 
to the meridian 30 minutes after it, on the 21st of January. 
These two form the upper end of the parallelogram. 

73. Rigel is a splended star of the 1st magnitude, in the left 
foot, on the W. and 15° S. of Bellatrix. Saiph is a star of the 
3d magnitude, in the right knee, $%° E. of Rigel. These two 
form the lower end of the parallelogram. 

sented on the maps ? How described by Manilius ? 71, Situation of Orion ? Number 
of visible stars ? Magnitudes? 72. What is the Ell and Yard ? What constitutes the 
outline of Orion? Where is JBellatrvsof Betelguese and magnitude? 73. Eiffel? 
Saiph t 



ORION. 43 



" First in rank 

The martial star upon his shoulder flames ; 
A rival star illuminates his foot ; 
And on his girdle beams a luminary 
Which, in vicinity of other stars, 
Might claim the proudest honors." 

74. There is a little triangle of three small stars in the head 
of Orion, which forms a larger triangle with the two in his 
shoulders. In the middle of the parallelogram are three stars 
of the 2d magnitude, in the belt of Orion, that form a straight 
line about 3° in length from N. W. to S. E. They are usually 
distinguished by the name of the Three Stars, because there are 
no other stars in the heavens that exactly resemble them in 
position and brightness. They are sometimes denominated the 
Three Kings, because they point out the Hyades and Pleiades 
on one side, and Sirius, or the Dog-star, on the other. In Job 
they are called the Bands of Orion ; while the ancient husband- 
men called them Jacob's rod, and sometimes the Rake. The 
University of Leipsic, in 1807, gave them the name of Napoleon. 
But the more common appellation for them, including those 
in the sword, is the Ell and Yard. They derive the latter name 
from the circumstance that the line which unites the " three 
stars' 7 in the belt measures just 3° in length, and is divided by 
the central star into two equal parts, like a yard-stick ; thus 
serving as a graduated standard for measuring the distances of 
stars from each other. When, therefore, any star is described 
as being so many degrees from another, in order to determine 
the distance, it is recommended to apply this rule. 

It is necessary that the scholar should task his ingenuity only a few evenings in apply- 
ing such a standard to the stars, before he will learn to judge of their relative distances 
with an accuracy that will seldom vary a degree from the truth. 

75. The northernmost star in the belt, called Mintika, is less 
than J-° S. of the equinoctial, and when on the meridian, is 
almost exactly over the equator. It is on the meridian, the 24th 
of January. The "three stars" are situated about 8° W. of 
the solstitial colure, and uniformly pass the meridian one hour 
and fifty minutes after the seven stars. There is a row of stars 
of the 4th and 5th magnitudes, S. of the belt, running down 
obliquely towards Saiph, which forms the sword. This row is 
also called the Ell because it is once and a quarter the length 
of the Yard or belt. 

74. What constitutes the head of Orion? What in the middle of the parallelogram? 
Names, and why? "Three stars?" "Three Kings?" "Bands of Orion," "Jacob's 
Hod," Napoleon," " Ell and Yard ? Use of the Ell and Yard ? 75. What said of Mm- 
tika? Of the " three stars?" What other row of stars? Forms what? Called what, 
and why ? 



44 ASTRONOMY. 

16. About 9° W. of Bellatrix, are eight stars, chiefly of the 
4th magnitude, iu a curved line running N. and S. with the con- 
cavity toward Orion ; these point out the skin of the lion in 
his left hand. Of Orion, on the whole, we may remark with 
Eudosia: — 

" He who admires not, to the stars is blind." 
HISTORY. 

According to some authorities, Orion was the son of Neptune and queen Euryale, a 
famous Amazonian huntress, and possessing the disposition of his mother, he became 
the greatest hunter in the world, and even boasted that there was not an animal on 
earth which he could not conquer. To punish this vanity, it is said that a scorpion 
sprung up out of the earth and bit his foot, that he died ; and that at the request of 
Diana he was placed among the stars directly opposite to the Scorpion that caused his 
death. Others say that Orion had no mother, but was the gift of the gods, Jupiter, 
Neptune, and Mercury, to a peasant of Boeotia, as a reward of piety, and that he was 
invested with the power of walking over the sea without wetting his feet. In strength 
and stature he surpassed all other mortals. He was skilled in the working of iron, from 
which he fabricated a subterranean palace for Vulcan ; he also walled in the coasts of 
Sicily against the inundations of the sea, and built thereon a temple to its gods. 

Orion was betrothed to the daughter of (Enopion, but he, unwilling to give up his 
daughter, contrived to intoxicate the illustrious hero and put out his eyes, on the sea- 
shore where he had laid himself down to sleep. Orion, finding himself blind when he 
awoke, was conducted by the sound to a neighboring forge, where he placed one of the 
workmen on his back, and, by his directions, went to a place where the rising sun was 
seen with the greatest advantage. Here he turned his face toward the luminary, and, 
as it is reported, immediately recovered his sight, and hastened to punish the perfidious 
cruelty of (Enopion. 

As the constellation Orion, which rises at noon about the 9th day of March, and sets at 
noon about the 21st of June, is generally supposed to be accompanied, at its rising, with 
great rains and storms, it became extremely terrible to mariners, in the early adven- 
tures of navigation. Virgil, Ovid, and Horace, with some of the Greek poets, make 
mention of this. 

Thus Eneas accounts for the storm which cast him on the African coast on his way to 
Italy:— 

" To that blest shore we steer'd our destined way, 
When sudden, dire Orion rous'd the sea ; 
All charg'd with tempests rose the baleful star, 
And on our navy pour'd his wat'ry war." 

To induce him to delay his departure, Dido's sister advises her to 
" Tell him, that, charged with deluges of rain, 
Orion rages on the wintry main." 

The name of this constellation is mentioned in the books of Job and Amos, and m 
Homer. The inspired prophet, penetrated like the psalmist of Israel with the omni- 
science and power displayed in the celestial glories, utters this sublime injunction : " Seek 
Him that maketh the seven stars and Orion, and turneth the shadow of death into 
morning." Job also, with profound veneration, adores his awful majesty who " com- 
mandeth the sun and sealeth up the stars ; who alone spreadeth out the heavens, and 
maketh Arcturus, Orion, and Pleiades, and the chambers of the south :" and in another 
place, the Almighty demands of him — " Knowest thou the ordinances of heaven? Canst 
thou bind the sweet influences of the Pleiades, or loose the bands of Orion ; canst thou 
bring forth Mazzaroth in his season, or canst thou guide Arcturus with his sons?" 

Calmet supposes that Mazzaroth is here put for the whole order of celestial bodies in 
the Zodiac, which, by their appointed revolutions, produce the various seasons of the 
year, and the regular succession of day and night. Arcturus is the name of the prin- 
cipal star in Bootes, and is here put for the constellation itself. The expression, his sons, 
doubtless refers to Asterion and Chara, the two greyhounds, with which he seems to be 
pursuing the Great Bear around the North pole. 

76. What stars mentioned west of Bellatrix? Remark respecting Orion? 

History.— Story of parentage? Disposition and boasting? Punishment? What 
other account? What mention of by Virgil? By Job and Homer? Supposition of 
Calmet? What meant by " Arcturus and his sons ?" 



LEPUS. 45 



TELESCOPIC OBJECTS. 

1. a Orionis (Betelguese) — R. A. 5h. 46m. 30s. ; Dec. N. 7° 22' 3'. A 1, orange tint ; 
B 11, bluish. 

2. (3 Orionis (Eigel)— R. A. 5h. 6m. 51s ; Dec. S. 8° 23' 5". A 1, pale yellow ; B 9, 
sapphire blue. Map VIII. Fig. 3. 

3. j Orionis (Bellatriti) — R. A. 5h. 16m. 33s. ; Dec. N. 6° 12'. A fine star, with a 
minute distant companion. A 2, pale yellow ; B 15, grey. 

4. d Orionis (Mintaka) — A coarse double star in the girdle of the figure ; R. A. 5h. 
23m. 50s. ; Dec. S. 0° 25' 4". A 2, white ; B 7, pale violet. 

5. e Orionis {Alnilam) in the centre of his belt ; R. A. 5h. 28m. 06s. ; Dec. S. 1° IS' 6". 
A 223, white and nebulous ; B. 10, pale blue. 

6. t, Orionis {Alnitah) the last or lowest in the belt; R. A. 5h.32m. 41s. ; Dec. S. 2° 02'. 
A fine triple star. A 3, topaz yellow ; B 6%, light purple ; and C 10, gray. 

7. A minute double star and cluster, in Orion's left hand ; R. A. 5h. 59m. 25s. ; Dec. 
N. 13° 58' 6". A 723, B 823, both lucid white. 

8. Another double star in a cluster, in the left shoulder; R. A. 6h. 03m. 35s. ; Dec. N. 
5° 28' 9". A 93^ and B 10, both pale yellow. A tolerably rich cluster, with numerous 
stragglers. 

9. A planetat nebula, of a bluish white tint, on the nape of Orion's neck — small, pale, 
but quite distinct. R. A. 5h. 33m. 21s. ; Dec. N. 9° 00' 2". 

10. Two stars " in a wispy nebula," just above the left hip ; R. A. 5h. 3Sm. 33s. ; Dec. 
N. 0° 00' 7°. A 823 and B. 9, both white. A singular mass, between two small stars, about 
equi-distant, in a blankish part of the heavens. 

11. The great nebula of Orion — The most conspicuous nebula in all the heavens. It 
is situated in the sicord of Orion, below the middle star of the belt ; R. A. 5h. 27m. 25s.; 
Dec. S. 5° 30'. For its position in the constellation see Map VIII., Fig. 31. It may be 
seen with a common telescope. There is an apparent opening in one side of this nebula, 
through which, as through a window, we seem to get a glimpse of other heavens, and 
brighter regions. (Map VIII., Fig. 32.) 

12. The middle star in the sword is in the midst of this nebula, and with powerful tele- 
scopes is found to be sextuple. The writer has often seen the fifth star with a 6-inch 
refractor. These stars constitute the Trapezium of Orion. The region around this 
nebula is rich in stars, as shown on Map VIII., Fig. 33. 



LEPUS (THE HARE).— MAP III. 

7 T. This constellation is situated directly south of Orion, and 
comes to the meridian at the same time ; namely, on the 24th 
of January. It has a mean declination 18° S., and contains 19 
small stars, of which, the four principal ones are of the 3d magni- 
tude. It may be readily distinguished by means of four stars 
of the 3d magnitude, in the form of an irregular square, or 
trapezium. 

78. Zeta, of the 4th magnitude, is the first star, and is 
situated in the back, 5° S. of Saiph, in Orion. About the same 
distance below Zeta are the four principal stars, in the legs and 
feet. These form the square. They are marked Alpha, Beta, 
Gamma, Delta. 

Telescopic Objects.— Alpha ? Beta? Gamma? Delta, &c? What double stars? 
Nebulae ? Point out on the map ? 

77. Location of Lepus? Number and magnitude of stars? How may it be distin- 
guished ? 78. Size and situation of Zeta ? Other principal stars ? How marked on 
the map ? 



46 ASTRONOMY. 

79. Alpha, otherwise called Arneb, and Beta form the N. W. 
end of the trapezium, and are about 3° apart. Gamma and 
Delta form the S. B. end, and are about 2£° apart. The upper 
right-hand one, which is Arneb, is the brightest of the four, and 
is near the centre of the constellation. Four or five degrees S. 
of Rigel are four very minute stars, in the ears of the Hare. 

history. 

This constellation is situated about 18° west of the Great Dog, which, from the motion 
of the earth, seems to be pursuing it, as the Greyhounds do the Bear, round the Circuit 
of the skies It was one of those animals which Orion is said to have delighted in hunt- 
ing, and which, for this reason, was made into a- constellation and placed near him 
among the stars. 

TELESCOPIC OBJECTS. 

1. a Lepoeis {Arneb) — A distant double star ; R, A. 5h. 25m. 40s. ; Dec. S. 17° 56' 05". 
A 3%, pale yellow ; B 9)3, grey. 

2. d Leporis {JSfihal) — A star with a distant telescopic companion ; R. A. 5h. 21m. 23s. ; 
Dec. S. 20° 53' 05". A 4, deep yellow ; B 11, blue. 

3. y Leporis — A wide triple star in a barren field; R. A. 5h. 37m. 48s.; Dec. S. 22" 
30' 02". A 4, light yellow ; B 6Jg, pale green ; C 13, dusky. 

4. i Leporis — A delicate double star in the Hare's left ear ; R. A. 6h. 04m. 50s. ; Dec. 
S. 12* 03' 09". A 4%, white ; B 12, pale violet, with a reddish distant star nearly north. 

5. K Leporis — A close double star, at the root oS-the left ear; R. A. 5h. 5m. 51s. ; Dec. 
S. 13° OS'. A 5, pale white ; B 9, clear grey. 

6. A bright stellar nebula, under the Hare's feet ; R. A. 5h. 17m. 50s. ; Dec. S. 24° 39' 
09". A fine object of a milky white tinge, and blazing towards the centre. Herschel 
describes it as " a beautiful cluster of stars, nearly 3' in diameter, of a globular form, 
and extremly rich." An imaginary line run from Betelguese before a Leporis, and over 
8, will hit this object about 4° south-west of the latter. 



COLUMBA (noah's dove).— MAP III. 

80. This constellation is situated about 16° S. of the Hare, 
and is nearly on the same meridian with the " Three Stars," in 
the belt of Orion. It contains only 10 stars ; one of the 2d, 
one of the 3d, and two of the 4th magnitudes ; of these Phaet 
and Beta are the brightest, and are about 2^-° apart. Phaet, 
the principal star, lies on the right, and is the highest of the 
two ; Beta may be known by means of a smaller star just east 
of it, marked Gamma. A line drawn from the easternmost star 
in the belt of Orion, 32° directly south, will point out Phaet ; it 
is also 11-^° S. of the lower left-hand star in the square of the 
Hare, and makes with Sirius and Naos, in the ship, a large equi- 
lateral triangle. 

79. What other name has Alpha ; and with Beta what does it form? What further 
description ? 

History. — Why was Lepus placed in the heavens ? 

Telescopic Objects. — Alpha? Beta? Gamma? Iota? Kappa? Nebula? 

80. Situation of Columba ? Number and size of stars ? The two brightest, and situa- 
tion? How find Phaet ? What figure does it help to form? With what other stars ? 



ERIDANUS. 47 



HISTORY. 

This constellation is so called in commemoration of the dove which Noah " sent forth 
to sec if the waters were abated from off the face of the ground," after the ark had 
rested on mount Ararat. " And the dove came in to him in the evening, and lo, in her 
mouth was an olive leaf plucked off. 

' The surer messenger, 



A dove sent forth once and again to spy 
Green tree or ground, whereon his foot may light : 
The second time returning in his bill 
An olive leaf he brings, pacific sign !" 



ERIDANUS (the rivek po).— MAP III. 

81. This constellation meanders over a large and very irregu- 
lar space in the heavens. It is not easy, nor scarcely desirable, 
to trace out all its windings among the stars. Its entire length 
is not less than 130° ; which, for the sake of a more easy refer- 
ence, astronomers divide into two sections, the northern and 
the southern. That part of it which lies between Orion and the 
Whale, including the great bend about his paws, is distinguished 
by the name of the Northern stream • the remainder of it is 
called the Southern stream. 

82. The Northern stream commences near Rigel, in the foot of 
Orion, and flows out westerly, in a serpentine course nearly 40° 
to the Whale, where it suddenly makes a complete circuit, and 
returns back nearly the same distance towards its source, but 
bending gradually down toward the south, when it again makes 
a similar circuit to the S. W., and finally disappears below the 
horizon. 

West of Rigel there are five or six stars of the 3d and 4th magnitudes, arching up in a 
semi-circular form, and marking the first bend of the northern stream. About 8° below 
these, or 19° W. of Rigel, is a bright star of the 2d magnitude, in the second bend of the 
northern stream, marked Gamma. This star culminates 13 minutes after the Pleiades, 
and one hour and a quarter before Rigel. Passing Gamma, and a smaller star west of 
it, there are four stars nearly in a row, which bring us to the breast of Cetus. 8° N. of 
Gamma, is a small star named Kied, which is thought by some to be considerably nearer 
the earth than Sirius. 

Theemim, in the southern stream, is a star of the 3d magnitude, about 17° S. W. of 
the square in Lepus, and may be known by means of a smaller star 1° above it. Aeher- 
nar is a brilliant star of the 1st magnitude, in the extremity of the southern stream; 
but having 58° of S. declination, can never be seen in this latitude. 

83. The whole number of stars in this constellation is 84 ; of 
which, one is of the 1st magnitude, one of the 2d, and eleven 
are of the 3d. Many of these cannot be pointed out by verbal 
description ; they must be traced from the map. 

History. — Origin of this constellation ? 

81. What said of Eridanus? Length? How divided? 82. Trace the Northern 
Stream? Gamma? Theemim? Achernar? 83. Whole number of stars in Eridanus ? 



48 ASTRONOMY. 

84. In the upper part of the Northern stream, near the feet 
of Taurus, may be seen a modern, but now discarded constella- 
tion, of which Captain Smyth says: "Abbe Hell (who also 
placed Herschel's Telescope among the celestials) has squeezed 
in his Iiarpa Georgii, to compliment a sovereign of those realms ; 
having filched from Eridanus about thirty or forty stars, some 
of the 4th magnitude, for the purpose. 

HISTORY. 

Eridanus is the name of a celebrated river in Cisalpine Oaul, also called Padus. Its 
modern name is Po. Virgil calls it the king of rivers. The Latin poets have rendered 
it memorable from its connection with the fable of Phaeton, who, being a son of Phoebus 
and Clymene, became a favorite of Venus, who intrusted him with the care of one of 
her temples. This favor of the goddess made him vain, and he sought of his father a 
public and incontestable sign of his tenderness, that should convince the world of his 
origin. Phoebus, after some hesitation, made oath that he would grant him whatever 
he required, and no sooner was the oath uttered, than — 

" The youth, transported, asks without delay, 

To guide the sun's bright chariot for a day. 

The god repented of the oath he took, 

For anguish thrice his radiant head he shook; — 

My son, says he, some other proof require, 

Rash was my promise, rash was thy desire — 

Not Jove himself, the ruler of the sky, 

That hurls the three-forked thunder from above, 

Dares try his strength ; yet who as strong as Jove? 

Besides, consider what impetuous force 

Turns stars and planets in a different course. 

I steer against their motions ; nor am I 

Borne back by all the current of the sky : 

But how could you resist the orbs that roll 

In adverse whirls, and stem the rapid pole ?" 

Phoebus represented the dangers to which he would be exposed in vain. He under- 
took the aSrial journey, and the explicit directions of his father were forgotten. No 
sooner had Phaeton received the reins than he betrayed his ignorance of the manner 
of guiding the chariot. The flying coursers became sensible of the confusion of their 
driver, and immediately departed from the usual track. Phaeton repented too late of 
his rashness, and already heaven and earth were threatened with a universal confla- 
gration as the consequence, when Jupiter, perceiving the disorder of the horses, struck 
the driver with a thunderbolt, and hurled him headlong from heaven into the river 
Eridanus. His body, consumed with fire, was found by the nymphs of the place, who 
honored him with a decent burial, and inscribed this epitaph upon his tomb : — 
"Hie situs est P7iaeton, currus aurigapatemi: 
Queue si non tenuit, magnis tamen excidit ausis." 

His sisters mourned his unhappy end, and were changed by Jupiter into poplars. 
" All the long night their mournful watch they keep, 
And all the day stand round the tomb and weep." — Ovid. 
It is said the tears which they shed turned to amber, with which the Phoenicians 
and Carthaginians carried on in secrecy a most lucrative trade. The great heat pro- 
duced on the occasion of the sun's departing out of his usual course, is said to have 
dried up the blood of the Ethiopians, and turned their skins black; and to have pro- 
duced sterility and barrenness over the greater part of Libya. 

"At once from life and from the chariot driven, 
Th' ambitious boy fell thunderstruck from heaven." 
******* 

84. What discarded constellation mentioned? Is it on the map? Remark of Capt. 
Smyth? 

History. — Named after what? Modern name? Fable of Phaeton? Its evident 
allusion ? 



AURIGA. 49 

•'The breathless Phaeton, with flaming hair, 
Shot from the chariot like a falling star, 
That in a summer's evening from the top 
Of heaven drops down, or seems at least to drop, 
Till on the Po his blasted corpse was hurl'd, 
Far from his country, in the western world." 

The fable of Phaeton evidently alludes to some extraordinary heats which were 
experienced in a very remote period, and of which only this confused tradition has 
descended to later times. 

TELESCOPIC OBJECTS. 

1. /3 Eridani — A bright star with a distant telescopic companion, on the shin bone of 
Orion ; R. A. 4h. 59m. 59s. ; Dec. S. 5° 17' 9". A 3, topaz yellow ; B 12, pale blue. This 
star is just above Rigel, in the direction of the Hyades. 

2. y Eridani — A star with a distant companion ; R. A. 3h. 50m. 34s. ; Dec. S. 13° 58". 
A 22£, yellow ; B 10 pale grey. 

3. A milk, white nebula ; R. A. 3h. 83m. 02s. ; Dec. S. 19° 04' 8". Pale, distinct, round, 
and bright in the centre. 

4. A planetary nebula ; R. A. 4h. 06m. 50s. ; Dec. S. 13° 09' 1". About 4%° from y 
in the direction of Rigel. A splendid though not very conspicuous object, of a greyish 
white color. Map VIIT., Fig. 34, represents it in its best aspects, highly magnified, 
with four telescopic stars in the field, two of which point exactly towards the nebula. 



SOEPTEUM BRANDENBUEGIUM (sceptre of beandenbtjrg-). 
MAP III. 

85. This is a slender constellation, situated between the two 
streams of the River Po. It was constructed by Kirch, in 1688, 
and recognized by Bode a century afterwards; but is now gene- 
rally discarded, though retained on the map. It is composed of 
four stars of the 3d, 4th and 5th magnitudes, running north and 
south; and is usually included in Eridanus. 

AURIGA (the charioteer). — MAP III. 

86. The Charioteer, called also the Wagoner, is represented 
on the celestial map by the figure of a man in a reclining posture, 
resting one foot upon the horn of Taurus, with a goat and hex 
kids in his left hand, and a bridle in his right. 

It is situated N. of Taurus and Orion, between Perseus on 
the W. and the Lynx on the E. Its mean declination is 45° 
N. ; so that when on the meridian, it is almost directly, overhead 
in New England. It is on the same meridian with Orion, and 
culminates at the same hour of the night. Both of these con- 
stellations are on the meridian at 9 o'clock on the 24th of 

Telescopic Objects. — Beta ? Gamma ? Nebula ? Point out on the map. 

85. Describe the Sceptre of Brandenburgh? Situation? When and by whom consti- 
tuted? Is it recognized by astronomers? Number and magnitude of stars? 86. How 
is Auriga represented? Situation? When on the meridian? 



50 ASTRONOMY. 

January, and 1 hour and 40 minutes east of it on the 1st of 
January. 

81. The whole number of visible stars in Auriga, is 66, 
including one of the 1st and one of the 2d magnitude, which 
mark the shoulders. Capella is the principal star in this con- 
stellation, and is one of the most brilliant in the heavens. It 
takes its name from Capella, the goat, which hangs upon the 
left shoulder. It is situated in the west shoulder of Auriga, 24° 
E. of Algol, and 28° N. E. of the Pleiades. It may be known 
by a little sharp-pointed triangle formed by three stars, 3° or 4° 
this side of it, on the left. It is also 18° N. of El Nath, which 
is common to the northern horn of Taurus, and the right foot 
of Auriga. Capella comes to the meridian on the 19th of 
January, just 2|- minutes before Rigel, in the foot of Orion, 
which it very much resembles in brightness. 

Menkalina, in the east shoulder, is a star of the 2d magnitude, 7%° E. of Capella, and 
culminates the next minute after Betelguese, Zl%" S. of it. Theta, in the right arm, is a 
star of the 4th magnitude, 8° directly south of Menkalina. 

It may be remarked as a curious coincidence, that the two stars in the shoulders of 
Auriga are of the same magnitude, and just as far apart as those in Orion, and opposite 
to them. Again, the two stars in the shoulders of Auriga, with the two in the shoulders 
of Orion, mark the extremities of a long, narrow parallelogram, lying N. and S., and 
whose length is just five times its breadth. Also, the two stars in Auriga, and the 
two in Orion, make two slender and similar triangles, both meeting in a common point, 
halfway between them at El Nath, iu the northern horn of Taurus. 

Delta, a star of the 4th magnitude in the head of Auriga, is about 9° N. of the two in 
the shoulders, with which it makes a triangle, about half the height of those just alluded 
to, with the vertex at Delta. The two stars in the shoulders are therefore the base of 
two similar triangles, one extending about 9° N. to the head, the other 18° S. to the heel, 
on the top of the horn : both figures together resembling an elongated diamond. 

Delta in the head, Menkalina in the right shoulder, and Theta in the arm of Auriga, 
make a straight line with Betelguese in Orion, Delta in the square of the Hare, and Beta 
in Noah's Dove ; all being very nearly on the same meridian, 48 W. of the solstitial 
colure. 

" See next the Goatherd with his kids ; he shines 

With seventy stars, deducting only four, 

Of which Capella never sets to us. 

And scarce a star with equal radiance beams 

Upon the earth : two other stars are seen 

Due to the second order." — Eudosia. 

HISTORY. 

The Greeks give various accounts of this constellation ; some supposed it to be Erich- 
thonius, the fourth king of Athens, and son of Vulcan and Minerva, who awarded him a 
place among the constellations on account of his many useful inventions. He was of a 
monstrous shape. He is said to have invented chariots, and to have excelled all others 
in the management of horses. In allusion to this, Virgil has the following lines " — 
" Primus Erichthonius currus et quatuor ausus 
Jungere equos, rapidisque rotis insistere victor." 

Georgic. Lib. iii. p. 113. 

" Bold Erichthonius was the first who join'd 
Four horses for the rapid race design'd, 
And o'er the dusty wheels presiding sat." — Dryden. 



87. Number of stars visible? Magnitude and situation of Capella? How known? 
Menkalina? Delta compared with Theta? 
History. — The first supposition ? Second? Third? Opinion of Jamieson ? 



CAMELOPARDALUS. 51 

Other writers say that Bootes invented the chariot, and that Auriga was the son of 
Mercury, and charioteer to (Enoniaus, king of Pisa, and so experienced, that he rendered 
his horses the swiftest in all Greece. But as neither of these fables seems to account for 
the goat and her kids, it has been supposed that they refer to Amalthaea and her sister 
Melissa, who fed Jupiter, during his infancy, with goat's milk, and that, as a reward for 
their kindness, they were placed in the heavens. But there is no reason assigned for 
their being placed in the arms of Auriga, and the inference is unavoidable, that 
mythology is at fault on this point. 

Jamieson is of opinion that Auriga is a mere type or scientific symbol of the beautiful 
fable of Phaeton, because he was the attendant of Phoebus at that remote period when 
Taurus opened the year. 

TELESCOPIC OBJECTS. 

1. a Axjrigm (Capella) — A fine star with two distant companions, on the right shoulder- 
blade of Auriga ; R. A. 5h. 04m. 53s. ; Dec. N. 45° 49' 07". A 1, bright white ; B 12, pale 
blue ; C 9, grey. 

2. (3 Aurigjs (Henkalina) — A bright star in the left shoulder, with a distant com- 
panion ; R. A. 5h. 47m. 48s. ; Dec. N. 44° 55' 3". A 2, yellow; B 105$, bluish. 

3. A rich cluster of minute stars, on the left thigh ; R. A. 5h. 18m. 41s. ; Dec. N. 35* 
44' 9" A singular figure, somewhat like a cross. Find by a line from Rigel, northwards 
through (3 Tauri, and about 7° beyond. 

4. A resolvable nebula ; R. A. 5h. 20m. 51s. ; Dec. N. 34° 06' 9". Situated in a rich 
field of minute stars. 



CAMELOPABDALUS (the camelopaed).— MAP YI. 

88. This constellation was made by Hevelius out of the 
unformed stars which lay scattered between Perseus, Auriga, 
the head of Ursa Major, and the Pole star. It is situated 
directly N. of Auriga and the head of the Lynx, and occupies 
nearly all the space between these and the pole. It contains 58 
small stars ; the five largest of which are only of the 4th mag- 
nitude. 

89. The principal star lies in the thigh, and is about 20° from 
Capella, in a northerly direction. It marks the northern boun- 
dary of the temperate zone ; being less than one degree S. of 
the Arctic circle. There are two other stars of the 4th magni- 
tude, near the right knee, 12° N. E. of the first mentioned. 
They may be known by their standing 1° apart and alone. 

The other stars in this constellation are too small, and too much scattered to invite 
observation. 

HISTORY. 

The Camelopard is so called from an animal of that name, peculiar to Ethiopia. This 
animal resembles both the camel and the leopard. Its body is spotted like that of the 
leopard. Its neck is about seven feet long, its fore and hind legs from the hoof to the 
second joint, are nearly of the same length ; but from the second joint of the legs to the 
body, the fore legs are so long in comparison with the hind ones, that no person could sit 
upon its back without instantly sliding off, as from a horse that stood up on his hind feet. 

Telescopic Objects. — Alpha? Beta? Cluster? Nebulas? 

88. Origin of Camelopardalus ? Situation and extent ? Number and size of its stars ? 
89. Where is its principal star ? The next two ? How known ? 
History. — Any mythological story ? What said of the animal ? 



E.G. 



52 ASTRONOMY. 

TELESCOPIC OBJECTS. 

1. a Camelopardali — A neat double star between the hind feet of the animal, half way 
between a Persei and 6 in the head of Auriga ; R. A. 4h. 19m. 23s. ; Dec. N. 53° 33' 3". 
A 7%, white ; B 8%, sapphire blue. 

2. Another close double star, between the hind feet ; R. A. 4h. 27m. 18s. ; Dec. N. 53° 
09'. A 5%, yellow ; B. 7%, pale blue. 

3. A very delicate double star in the animal's hind hoof; R. A. 4h. 44m. 28s. ; Dec. N. 
53° 29' 3°. A 5, white ; B 13, orange. 

4. A fine double star in the lower part of the back of the neck; R. A. 4h. 46m. 19s. ; 
Dec. N. 79° 01' 8". A 5%, light yellow ; B 9, pale blue. 

5. A bright planetary nebula, of a bluish white tint, about 60" in diameter, in the 
nind flank of the animal, R. A. 4h. 53m. 29s. Dec. N. 60° 23' 5". A curious body, in a 
rich field of small star 3. 



CHAPTER IY. 

CONSTELLATIONS ON THE MERIDIAN IN FEBRUARY. 

THE LYNX.— MAPS III. AND VI. 

90. This constellation, like that of the Camelopard, exhibits 
no very interesting features by which it can be distinguished. It 
contains only a moderate number of inferior stars, scattered 
over a large space N. of Gemini, and between Auriga and Ursa 
Major. 

91. The whole number of stars in this constellation is 44, 

including only three that are so large as the 3d magnitude. 

The largest of these, near the mouth, is in the solstitial colure, 

14J° N. of Menkalina, in the E. shoulder of Auriga. The other 

two principal stars are in the brush of the tail, 3-j-° S. W. of 

another star of the same brightness in the mouth of the Lesser 

Lion, with which it makes a small triangle. Its centre is on 

the meridian at 9 o'clock on the 23d, or at half-past 1 on the 1st 

of February. 

telescopic objects. 

1. A close double star, in the nose of the Lynx ; R. A. 6h. 07m. 51s. ; Dec. N. 59° 25' 8". 
About 30° from the Pole star, on a line toward Sirius. A 6, and B 73£, both white. An 
elegant but difficult object. 

2. A close double star in the eye of the Lynx, between Dubhi and Capella ; R. A. 6h. 
88m. 57s. ; Dec. N. 59° 37' 6". A b%, golden yellow; B 7, purple. A delicate and pretty 
object. 

3. A coarse triple star on the animal's lower jaw; R. A. 6h. 12m. 50s. ; Dec. N. 58° 
29' 7". A. 6, orange tinge ; B 13, blue ; and C 9, pale garnet. 

4. A round nebula, in the Lynx, or fore paws of Leo Minor ; R. A. 9h. 14m. 82s. ; 
Dec. N. 35° 11' 9". It is pale white, sparkling in the centre. 

Telescopic Objects. — Alpha? What other double stars? Nebula? 
90. Describe the Lynx ? Situation ? 91. Number and size of its stars ? Where is the 
largest situated? The other two principal stars? 
Telescopic Objects. — What double stars ? Triple? Nebula 



GEMINI. 53 

TELESCOPIUM HERSCHELLII (heesohel's telescope).— 

MAP in. 

92. About midway between the body of the Lynx and Gemini, 
may be seen the rude figure of a refracting Telescope, with its 
stand. It was made out of a few unformed stars, by Abbe 
Hell, in honor of Sir William Herschel, but is now generally 
discarded. It is retained on the map more as a matter of history 
than to perpetuate it as a constellation. 

GEMINI (the twins).— MAP III. 

93. This constellation represents, in a sitting posture, the twin 
brothers, Castor and Pollux. It is the third sign, but fourth 
constellation in the order of the Zodiac, and is situated south of 
the Lynx, between Cancer on the east, and Taurus on the west. 

94. The plane of the Ecliptic passes through the centre of 
Gemini ; and as the earth moves round in her orbit from the first 
point of Aries to the same point again, the sun, in the mean- 
time, will appear to move through the opposite signs, or those which 
are situated right over against the earth, on the other side of her 
orbit. Accordingly, if we could see the stars as the sun appeared 
to move by them, we should see it passing over the constellation 
Gemini between the. 21st of June and the 23d of July; but we 
seldom see more than a small part of any constellation through 
which the sun is then passing, because the feeble lustre of the 
stars is obscured by the superior effulgence of the sun. 

When the sun is just entering the outlines of a constellation on the east, its western 
limit may be seen in the morning twilight, just above the rising sun. So when the sun 
has arrived at the western limit of a constellation, the eastern part of it may be seen 
lingering in the evening twilight, just behind the setting sun. Under other circum- 
stances, when the sun is said to be in, or to enter, a particular constellation, it is to be 
understood that that constellation is not then visible, but that those opposite to it are. 
For example : whatever constellation sets with the sun on any day, it is plain that the 
one opposite to it must be then rising, and continue visible through the night. Also, 
whatever constellation rises and sets with the sun to-day, will, six months hence, rise at 
sun-setting, and set at sun-rising. For example : the sun is in the centre of Gemini 
about the 6th of July, and must rise and set with it on that day ; consequently, six 
months from that time, or about the 4th of January, it will rise in the east, just when the 
sun is setting in the west, and will come to the meridian at midnight ; being then exactly 
opposite the sun. And as the stars gain upon the sun at the rate of two hours every 
month, it follows that the centre of this constellation will, on the 17th of February, come 
to the meridian three hours earlier, or at 9 o'clock in the evening. 

The sun is in the vernal equinox about the 21st of March, from whence it advances 

92. What said of Herschel's Telescope? Why perpetuated on the map? 93. How 
is Gemini represented ? Its order in the signs, &c. ? Situation? 94. How with respect 
to the Ecliptic ? What result from this fact? What remarks respecting the sun and 
constellations ? 



54 ASTRONOMY. 

through one sign or constellation every succeeding month thereafter; and that each 
constellation is one month in advance of the sign of that name: wherefore, reckon 
Pisces in March, Aries in April, Tam-us in May, and Gemini in June, &c, beginning with 
each constellation at the 21st, or 22d of the month. 

95. Gemini contains 85 stars, including two of the 2d, three 
of the 3d, and six of the 4th magnitudes. It is readily recog- 
nized by means of the two principal stars, Castor and Pollux, 
of the 1st and 2d magnitudes, in the heads of the Twins, about 
4-J° apart. 

There being only 11 minutes' difference in the transit of these two stars over the meri- 
dian, they may both be considered as culminating at 9 o'clock about the 24th of Febru- 
ary. Castor, in the head of Castor, is a star of the 1st magnitude, 4Jg° N. W. of Pol- 
lux, and is the northernmost and the brightest of the two. Pollux is a star of the 2d 
magnitude, in the head of Pollux, and is 4^° S. E. of Castor. This is one of the stars 
from which the moon's distance is calculated in the Nautical Almanac. 

" Of the famed Ledean pair, 

One most illustrious star adorns their sign, 
And of the second order shine twin lights." 

96. The relative magnitude or brightness of these stars has 
undergone considerable changes at different periods ; whence it 
has been conjectured by various astronomers that Pollux must 
vary from the 1st to the 3d magnitude. But Herschel, who 
observed these stars for a period of 25 years, ascribes the varia- 
tion to Castor, which he found to consist of two stars, very 
close together, the less revolving about the larger once in 342 
years and two months. 

Bradley and Maskelyne found that the line joining the two stars which form Castor 
was, at all times of the year, parallel to the line joining Castor and Pollux ; and that 
both of the former move around a common centre between them, in orbits nearly circu- 
lar, as two balls attached to a rod would do, if suspended by a string affixed to the cen- 
tre of gravity between them. 

" These men," says Dr. Bowditch, " were endowed with a sharpness of vision, and a 
power of penetrating into space, almost unexampled in the history of astronomy." 

91. About 20° S. W. of Castor and Pollux, and in a line 
nearly parallel with them, is a row of stars 3° or 4° apart, 
chiefly of the 3d and 4th magnitudes, which distinguish the feet 
of the Twins. The brightest of these is Alkena, in Pollux's 
upper foot ; the next small star S. of it, is in his other foot ; 
the two upper stars in the line next above Gamma, mark Cas- 
tor's feet. 

This row of feet is nearly two-thirds of the distance from Pollux to Betelguese in Orion, 
and a line connecting them will pass through Alhena, the principal star in the feet. 
About two thirds of the distance from the two in the head to those in the feet, and nearly 
parallel with them, there is another row of three stars about 6° apart, which mark the 
knees. 

95. Number of stars in Gemini? Magnitudes? How recognize this constellation? 
What said of the culmination of Castor, and of Pollux ? 96. Are they variable ? What 
did Bradley and Maskelyne ascertain ? Remark of Bowditch ? 97. What constitute 
the feet of Gemini ? Alhena ? How situated ? What mark the knees t 



GEMINI. 55 

98. There are, in this constellation, two other remarkable 
parallel rows, lying at right angles with the former ; one, lead- 
ing from the head to the foot of Castor, the brightest star being 
in the middle, and in the knee : the other, leading from the 
head to the foot of Pollux, the' brightest star, called Wasat, 
being in the body, and Zeta, next below it, in the knee. 

Wasat is in the ecliptic, and very near the center of the constellation. The two stars, 
Mu and Tejat, in the northern foot, are also very near the ecliptic ; Tejat is a small star 
of between the 4th and 5th magnitudes, 2° W. of Mu, and deserves to be noticed because 
it marks the spot of the summer solstice, in the tropic of Cancer, just where the sun is on 
the longest day of the year, and is, moreover, the dividing limit between the torrid and 
the N. temperate zone. 

Projms, also in the ecliptic, 2%° W. of Tejat, is a star of only the 5th magnitude, but 
rendered memorable as being the star which served for many years to determine the 
position of the planet Herschel, after its first discovery. 

HISTORY. 

Castor and Pollux were twin brothers, sons of Jupiter, by Leda, the wife of Tyndarus, 
king of Sparta. The manner of their birth was very singular. They were educated at 
PalTena, and afterwards embarked with Jason in the celebrated contest for the golden 
fleece, at Colchis; on which occasion they behaved with unparalleled courage and 
bravery. Pollux distinguished himself by his achievements in arms and personal 
prowess, and Castor in equestrian exercises and the management of horses ; whence they 
are represented, in the temples of Greece, on white horses, armed with spears, riding 
side by side, their heads crowned with a petasus, on whose top glitters a star. Among 
the ancients, and especially among the Romans, there prevailed a superstition that 
Castor and Pollux often appeared at the head of their armies, and led on their troops to 
battle and to victory. 

" Castor and Pollux, first In martial force, 
One bold on foot, and one renown'd for horse. 
Fair Leda's twins in time to stars decreed, 
One fought on foot, one curb'd the fiery steed." — Virgil. 

" Castor alert to tame the foaming steed, 
And Pollux strong to deal the manly deed." — Martial. 

The brothers cleared the Hellespont and the neighboring seas from pirates after their 
return from Colchis ; from which circumstance they have ever since been regarded as 
the friends and protectors of navigation. In the Argonautic expedition during a violent 
storm, it is said two flames of fire were seen to play around their heads, and immediately 
the tempest ceased, and the sea was calm. From this circumstance, the sailors inferred, 
that whenever both fires appeared in the sky, it would be fair weather ; but when only 
one appeared, there would be storms. 

St. Paul, after being wrecked on the island of Melita, embarked for Rome "in a ship 
whose sign was Castor and Pollux;" so formed, no doubt, in accordance with the popu- 
lar belief that these divinities presided over the science and safety of navigation. 

They were initiated into the sacred mysteries of Cabiri, and into those of Ceres at 
Eleusis. They were invited to a feast at which Lynceus and Idas were going to celebrate 
their nuptials with Phcebe and Telaria, the daughters of Leucippus, brother to Tyndarus. 
They became enamored of the daughters, who were about to be married, and resolved to 
supplant their rivals : a battle ensued, in which Castor killed Lynceus, and was himself 
killed by Idas. Pollux revenged the death of his brother by killing Idas ;" but being him- 
self immortal and most tenderly attached to his deceased brother, he was unwilling to 
survive him; he therefore entreated Jupiter to restore him to life, or to be deprived him- 
self of immortality ; wherefore, Jupiter permitted Castor, who had been slain, to share 
ttie immortality of Pollux ; and consequently as long as the one was upon earth, so long 
was the other detained in the infernal regions, and they alternately lived and died every 
day. Jupiter also further rewarded their fraternal attachment by changing them both 

93. What other remarkable rows of stars in Gemini ? Situation of Wasat f Of Tejat ? 
Of PropvA t 

History. — Myth of the parentage of Gemini ? Their achievements ? Roman supersti- 
tion ? That of sailors ? Allusion of St. Paul ? Story of the fatal wedding ? 



56 ASTRONOMY. 

into a constellation under the name of Gerrvmi, Twms, which, it is strangely pretended, 
never appear together, but when one rises the other sets, and so on, alternately. 
" By turns they visit this ethereal sky, 

And live alternate, and alternate die." — Homer. 
" Pollux, offering his alternate life, 
Could free his brother, and could daily go 
By turns aloft, by turns descend below." — Virgil. 
Castor and Pollux were worshiped both by the Greeks and Romans, who sacrificed 
white lambs upon their altars. In the Hebrew Zodiac, the constellation of the Twins 
refers to the tribe of Benjamin. 

TELESCOPIC OBJECTS. 

1. a Geminorum (Castor) — A neat double star ; K. A. 7h. 24m. 23s. ; Dec. N. 32° 14'- 
A 3. bright white ; B3^, pale white ; with a third star of the 11th magnitude about 72" 
distant. A Binary System, with a probable period of 232 years. A beautiful object, and 
easily found. Map VIII., Fig. 4. 

2. /? Geminorum— A quadruple star in the eye of Pollux, R. A. 7h. 35m. 31s.; Dec. 
N. 28° 25' 4". A 2, orange tinge ; B 12, ash-colored ; 11, pale violet, with another 
minute companion visible with the best instruments. 

3. y Oeminorum (Alhena) — A coarse triple star, in the right foot of Pollux; R. A. 
6h. 28m. 28s. ; Dec. N. 16° 31' 8". ; A 3, brilliant white; B 13, and C 12, both pale plum 
color. It is on a line from Rigel to ft Oeminorum, and nearest the former. 

4. J Oeminorum ( Wdsat) — A double star on the right hip of Pollux ; R. A. 7h. 10m. 
34s. ; Dec. N. 22° 16' 3". A 3%, pale white ; B 9, purple. 

5. e Geminorum (Melucta) — A star with a distant companion, on Castor's right knee ; 
R. A. 6h. 34m. 05s. ; Dec. N. 25° 16' 9". A 3, white ; B 9%, cerulean blue. 

6. £ Geminorum — A coarse triple star on the right knee of Pollux ; R. A. 6h. 54m. 3Ts. ; 
Dec. N. 20° 47' 9". A 4, pale topaz ; B 8, violet ; C 13, grey. 

7. A cluster, near the right foot of Castor ; R. A. 5h. 59m. 01s. ; Dec. N. 24° 21' 3". A 
gorgeous field of stars from the 9th to the 16th magnitudes. 

8. A cluster in the calf of Pollux's right leg ; R. A. 6h. 45m. 56s. ; Dec. N. 18° 10' 5'. 
A faint angular group of extremely small stars, in a rich region, but seen with difficulty. 
See Map VIII., Fig. 35. 

9. A compressed cluster under the left shoulder of Pollux; one-third the distance 
from j3 Geminorum, to (3 Canis Minoris ; R. A. 7h. 28m. 57s. ; Dec. N. 21° 55' 7". A 
faint object about 12 in diameter, with a small star near the centre. Map VIII., Fig. 36. 



CAKtS MINOR (the little dog).— MAP III. 

99. This small constellation is situated about 5° N. of the equi- 
noctial, and midway between Canis Major and the Twins. It 
contains 14 stars, of which two are very brilliant. The brightest 
star is called Procyon. It is of the 1st magnitude, and is about 
4° S. E. of the next brightest, marked Gomelza, which is of the 
3d magnitude. These two stars resemble the two in the head 
of the Twins. Procyon, in the Little Dog, is 23° S. of Pollux 
in G-emini, and Gomelza is about the same distance S. of Castor. 

100. A great number of geometrical figures may be formed 
of the principal stars in the vicinity of the Little Dog. For 
example : Procyon is 23° S. of Pollux, and 26° E. of Betef- 

Telescopic Objects.— Alpha ? Beta? Gamma? Delta, &c. ? Clusters? Which 
shown on the map? 

99. Where is Canis Minor situated? Number of stars ? Name of brightest? Mag- 
nitude? Next brightest? What do these two resemble? 100. What said of geome- 
trical figures ? Of the name Procyon t Its import? 



CANIS MINOR. 57 

guese, and forms with them a large right-angled triangle. 
Again, Procyon is equi-distant from Betelguese and Sirius, and 
forms with them an equilateral triangle whose sides are each 
about 26°. If a straight line, connecting Procyon and Sirius, 
be produced 23° farther, it will point out Phaet, in the Dove. 

Procyon is often taken for the name of the Little Dog, or for the whole constellation, 
as Sirius is for the greater one ; hence it is common to refer to either of these constel- 
lations by the name of its principal star. Procyon comes to the meridian 53 minutes 
after Sirius, on the 24th of February ; although it rises, in this latitude, about half an 
hour before it. For this reason, it was called Procyon, from two Greek words which 
signify {Ante Canis) " before the dog." 

HISTORY. 

The Little Dog, according to Greek fable, is one of Orion's hounds. Some suppose it 
refers to the Egyptian god Anubis, which was represented with a dog's head ; others to 
Diana, the goddess of hunting ; and others, that it is the faithful dog Maera, which 
belonged to Icarus, and discovered to his daughter Erigone the place of his burial. 
Others, again, say it is one of Actason's hounds that devoured their master, after Diana 
had transformed him into a stag, to prevent, as she said, his betraying her. 
" This said, the man began to disappear 
By slow degrees, and ended in a deer. 
Transform'd at length, he flies away in haste, 
And wonders why he flies so fast 
But as by chance, within a neighb'ring brook, 
He saw his branching horns, and alter'd look, 
Wretched Acteon ! in a doleful tone 
He tried to speak, but only gave a groan ; 
And as he wept, within the watery glass, 
He saw the big round drops, with silent pace, 
Run trickling down a savage, hairy face. 
What should he do ? or seek his old abodes, 
Or herd among the deer, and skulk in woods? 
As he thus ponders, he behind him spies 
His opening hounds, and now he hears their cries. 
From shouting men, and horns, and dogs he flies. 
When now the fleetest of the pack that press'd 
Close at his heels, and sprung before the rest, 
Had fastened on him, straight another pair 
Hung on his wounded side, and held him there, 
Till all the pack came up, and every hound 
Tore the sad huntsman groveling on the ground." 
It is not difficult to deduce the moral of this fable. The selfishness and caprice of 
human friendship furnish daily illustrations of it. While the good man, the philanthro- 
pist, or the public benefactor, is in affluent circumstances, and, with a heart to devise, 
has the power to minister blessings to his numerous beneficiaries, his virtues are the 
general theme ; but when adverse storms have changed the ability, though they could 
not shake the will of their benefactor, he is straightway pursued, like Actaeon, by his own 
hounds ; and, like Acteon, he is "torn to the ground" by the fangs that fed upon his 
bounty. 

It is most probable, however, that the Egyptians were the inventors of this con- 
stellation ; and as it always rises a little before the Dog Star, which, at a particular 
season, they so much dreaded, it is properly represented as a little watchful crea- 
ture, giving notice like a faithful sentinel of the other's approach. 

TELESCOPIC OBJECTS. 
* 1. a Canis Minoris {Procyon) — A bright star in the loins of the dog with a distant 
companion ; R. A. 7h. 30m. 55s ; Dec. N. 5° 37' 8°. A 1%, yellowish white ; B 8, orange 
tint. Several small stars in the field. 

History. — What is the Little Dog supposed to represent ? Fable of Actaeon ? Its 
moral ? Who probably invented this constellation ? To represent what? 
Telescopic Objects. — Alpha ? Beta ? Double star ? Triple ? 



58 ASTRONOMY. 

2. j3 Canis Minoris (Gomelsa) — A wide triple star in theneck; R. A. 7h. 18m. 28s. ; 
Dec. N. 8° 36' 4". A 3, white ; B 12, orange ; C 10, flushed— the last coarsely double with 
one of the same magnitude. Other stars in the field. 

3. A close double star, in a fine vicinity in the loins ; R. A. 7h. 31m. 37s. ; Dec. N. 5° 
35' 7". A 7, white ; B 8, ash-colored, with a minute blue star 2' distant. 

4. A wide triple star, 6° S. E. of Procyon ; R. A. 7h. 50m. 03s. ; Dec. N. 2° 38' 8'. A 
6, pale white ; B 8, bluish ; C 9, blue. 



MONOCEROS (the unicorn).—- MAP III. 

101. This is a modern constellation, made out of the unformed 
stars of the ancients that lay scattered over a large space of 
the heavens between the two Dogs. It extends a considerable 
distance on each side of the equinoctial, and its centre is on the 
same meridian with Procyon. 

102. It contains 31 small stars, of which the seven principal 
ones are of only the 4th magnitude. Three of these are situ- 
ated in the head, 3° or 4° apart, forming a straight line N. E. 
and S. W. about 9° E. of Betelguese in Orion's shoulder, and 
about the same distance S. of Albena in the foot of the twins. 

The remaining stars in this - constellation are scattered over a 
large space, and being very small, are unworthy of particular 
notice. 

HISTORY. 

The Monoceros is a species of the Unicorn or Rhinoceros. It is about the size of a 
horse, with one Avhite horn growing out of the middle of its forehead. It is said to exist 
in the wilds of Ethiopia, and to be very formidable. 

Naturalists say that, when pursued by the hunters, it precipitates itself from the 
tops of the highest rocks, and pitches upon its horn, which sustains the whole force of 
its fall, so that it receives no damage thereby. Sparmann informs us, that the figure of 
the unicorn, described by some of the ancients, has been found delineated on the surface 
of a rock in Caffraria ; and thence conjectures that such an animal, instead of being 
fabulous, as some suppose, did once actually exist in Africa. Lobo affirms that he has 
seen it. 

The rhinoceros, which is akin to it, is found in Bengal, Siam, Cochin China, part of 
China Proper, and the isles of Java and Sumatra. 

TELESCOPIC OBJECTS. 

1. A most delicate double star ( /), in the Unicorn's eye ; R. A. 6h. 26m. 06s. ; Dec. N. 
7° 41' 05". A 6, yellowish white : B 16, dusky. A difficult object. 

2. A neat double star (Jj), in the nostril, 7}£° east of Betelguese; R. A. 6h. 15m. 17s. ; 
Dec. N. 4° 40' 01". A 5%, golden yellow ; B 8, lilac. 

3. A fine triple star in the right fore-leg; R. A. 6h. 21m. 04s. ; Dec. S. 6° 56' 01°. A 
6H, white ; B 7, and C 8, both pale white. A ray shot from the Bull's eye through Bella- 
trix, and rather more than as far again, will pick it up. Supposed by Herschel to be a 
triple system, periods A B 17,000 ys. B C 1000. Shown double only on the map of 
the constellations. Telescopic view, Map VIII., Fig. 5. 

4. A delicate triple star, in a magnificent stellar field, between the Unicorn's ears ; 
R. A. 6h. 32m. 10s. ; Dec. N. 10° 02' 02". One-third the distance from Procyon to Alde- 
'baratt. A 6, greenish ; B 9%, pale grey ; C 15, blue. A fine object. 

101. Character and situation of Monoceros? Extent? 102. Number and size of its 
stars ? How three of the largest situated? 
History. — What said of the animal itself? Is it not wholly fabulous ? 
Telescopic Objects. — Double stars ? Triple ? Any shown on the map? 



CANIS MAJOR. 59 



CANIS MAJOR (the geeat dog).— MAP HI. 

103. This interesting constellation is situated southward and 
eastward of Orion, and is universally known by the brilliance 
of its principal star, Sirius, which is apparently the largest and 
brightest in the heavens. It glows in the winter hemisphere with 
a lustre which is unequaled by any other star in the firmament. 
Its distance from the earth, though computed at 20 millions 
of millions of miles, is supposed to be less than that of any other 
star : a distance, however, so great that a cannon ball, which 
flies at the rate of 19 miles a minute, would be two millions of 
years in passing over the mighty interval ; while sound, moving 
at the rate of 13 miles a minute, would reach Sirius in little less 
than three millions of years. 

It may be shown in the same manner, that a ray of light, which occupies only 8 minutes 
and 13 seconds in coming to us from the sun, which is at the rate of nearly two hundred 
thousand miles a second, would be 3 years and 82 days in passing through the vast space 
that lies between Sirius and the earth. Consequently, were it blotted from the heavens, 
its light would continue visible to us for a period of 3 years and 82 days after it had 
ceased to be. 

If the nearest stars give such astonishing results, what shall we say of those which are 
situated a thousand times as far ~beyond these, as these are from us ? 

104. In the remote ages of the world, when every man was 
his own astronomer, the rising and setting of Sirius, or the Dog 
Star, as it is called, was watched with deep and various solici- 
tude. The ancient Thebans, who first cultivated astronomy in 
Egypt, determined the length of the year by the number of its 
risings. The Egyptians watched its rising with mingled appre- 
hensions of hope and fear ; as it was ominous to them of agri- 
cultural prosperity or blighting drought. It foretold to them 
the rising of the Nile, which they called Siris, and admonished 
them when to sow. 

105. The Romans were accustomed yearly to sacrifice a dog 
to Sirius, to render him propitious in his influence upon their 
herds and fields. The eastern nations generally believed the 
rising of Sirius would be productive of great heat on the earth. 

Thus Virgil :— 

" Turn steriles exurere Sirius agros ; 

Ardebant herbae, et victum seges segra negabat." 

"Parched was the grass, and blighted was the corn: 

Nor 'scape the beasts ; for Sirius from on high, 
With pestilential heat infects the sky." 



103. Situation of Canis Major? How known? Supposed distance of Sirius ? Illus- 
trated by the speed of a cannon ball ? Of light ? 104. How was Sirius regarded by the 
ancients? Use made of it by the Thebans? The Egyptians? 105. Practice of the 
Romans ? 

3* 



60 ASTRONOMY. 

106. Accordingly, to that season of the year when Sirius rose 
with the sun and seemed to blend its own influence with the 
heat of that luminary, the ancients gave the name of Dog-days, 
{Dies canicularis.) At that remote period the Dog-days com- 
menced on the 4th of August, or four days after the summer 
solstice, and lasted forty days, or until the 14th of September. 
At present the dog-days begin on the 3d of July, and continue 
to the 11th of August, being one day less than the ancients 
reckoned. 

lOt. Hence, it is plain that the Dog-days of the moderns 
have no reference whatever to the rising of Sirius, or any other 
star, because the time of their rising is perpetually accelerated 
by the precession of the equinoxes : they have reference then 
only to the summer solstice, which never changes its position in 
respect to the seasons. 

The time of Sirius' rising varies with the latitude of the place, and in the same latitude, 
is sensibly changed after a course of years, on account of the precession of the equinoxes. 
This enables us to determine with approximate accuracy, the dates of many events of 
antiquity, which cannot be well determined by other records. We do not know, for 
instance, in what precise period of the world Hesiod nourished. Yet he tells us in his 
Opera et Dies, lib. ii. v. 185, that Arcturus in his time rose heliacally, 60 days after the 
winter solstice, which then was in the 9th degree of Aquarius, or 39° beyond its present 
position. Now 39° : 5034"=2794 years since the time of Hesiod, which corresponds very 
nearly with history. 

108. When a star rose at sun-setting, or set at sun-rising, it 
was called the Achronical rising or setting. When a planet or 
star appeared above the horizon just before the sun, in the morn- 
ing, it was called the Heliacal rising of the star ; and when it 
sunk below the horizon immediately after the sun, in the evening, 
it was called the Heliacal setting. 

According to Ptolemy, stars of the first magnitude are seen rising and setting when the 
sun is 12° below the horizon ; stars of the 2u magnitude require the sun's depression to 
be 13° ; stars of the 3d magnitude, 14' , and so on, allowing one degree for each magni- 
tude. The rising and setting of the stars described in this way, since this mode of 
description often occurs in Hesiod, Virgil, Columella, Ovid, Pliny, &c, are called poetical 
rising and setting. They served to mark the times of religious ceremonies, the seasons 
allotted to the several departments of husbandry, and the overflowing of the Nile. 

109. The student may be perplexed to understand how the 
Dog Star, which he seldom sees till mid-winter, should be asso- 
ciated with the most fervid heat of summer. This is explained 
by considering that this star, in summer, is over our heads in 
the daytime, and in the lower hemisphere at night. As " thick 
the floor of heaven is inlaid with patines of bright gold," by day, 

106. Origin of the phrase Dog-days? When did they begin in the time of Virgil? At 
what time now ? 107. What inference from these facts ? What variation in the time 
of Sirius' rising ? What calculation by knowing the time when Sirius rose, at any period ? 
108. What are the Achronical and Heliacal rising or setting of a star or planet ? Re- 
mark of Ptolemy in regard to rising and setting of the stars ? 109. How is it that 
Sirius, a winter star, is associated with the heat of summer ? 



CANIS MAJOR. 61 

as by night ; but on account of the superior splendor of the sun, 
we cannot see them. 

110. Sirius is situated nearly S. of Alhena, in the feet of the 
Twins, and about as far S. of the equinoctial as Alhena is N. 
of it. It is about 10° E. of the Hare, and 26° S. of Betel- 
guese in Orion, with which it forms a large equilateral triangle. 
It also forms a similar triangle with Phaet in the Dove, and 
Naos in the Ship. These two triangles being joined at their 
vertex in Sirius, present the figure of an enormous X, called by 
some, the Egyptian X. Sirius is also pointed out by the direc- 
tion of the Three Stars in the belt of Orion. Its distance from 
them is about 23°. It comes to the meridian at 9 o'clock on 
the 11th of February. 

111. Mirzam, in the foot of the Dog, is a star of the 2d mag- 
nitude, 5£° W. of Sirius. A little above, and 4° or 5° to the 
left, there are three stars of the 3d and 4th magnitudes, forming 
a triangular figure somewhat resembling a dog's head. The 
brightest of them, on the left, is called Muliphen. It entirely 
disappeared in 1670, and was not seen again for more than 20 
years. Since that time it has maintained a steady lustre. 

112. Wesen is a star of between the 2d and 3d magnitudes, 
in the back, 11° S. S. E. of Sirius, with which, and Mirzam in 
the paw, it makes an elongated triangle. The two hinder feet 
are marked by Naos and Lambda, stars of the 3d and 4th 
magnitudes, situated about 3° apart, and 12° directly S. of the 
fore foot. This constellation contains 31 visible stars, including 
one of the 1st magnitude, four of the 2d, and two of the 3d ; 
all of which are easily traced out by the aid of the map. 

HISTORY. 

Manilius, a Latin poet who flourished in the Augustan age, wrote an admirable poem, 
in five books, upon the fixed stars, in which he thus speaks of this constellation : 
" All others he excels ; no fairer light 
Ascends the skies, none sets so clear and bright." 
But Eudosia best describes it — 

" Next shines the Dog with sixty-four distinct ; 
Famed for pre-eminence in envied song, 
Theme of Homeric and Virgilian lays ; 
His fierce mouth flames with dreaded Sirius ; 
Three of his stars retire with feeble beams." 
According to some mythologists, this constellation represents one of Orion's hounds, 
Which was placed in the sky, near this celebrated huntsman. Others say it received its 
name in honor of the dog given by Aurora to Cephalus, which surpassed in speed all the 

110. Situation of Sirius ? What triangles ? 111. Position and size of Mirzam ? 
Other stars? Muliphen? 112. Wesen ? What other stars ? Whole number? 

History. — What classical description of Canis Major? What different accounts of its 
origin ? 



62 ASTRONOMY. 

animals of Lis species. Cephalus, it is said, attempted to prove this by running him 
against a fox, which, at that time, was thought to be the fleetest of all animals. After 
they had run together a long time, without either of them obtaining the victory, it is 
said that Jupiter was so much gratified at the fleetness of the dog, that he assigned him 
a place in the heavens. 

But the name and form of this constellation are, no doubt, derived from the Egyp- 
tians, who carefully watched its rising, and by it judged of the swelling of the Nile, 
which they called Siris, and, in their hieroglyphical manner of writing, since it was, as 
it were, the sentinel and watch of the year, represented it under the figure of a dog. 
They observed that when Sirius became visible in the east, just before the morning dawn, 
the overflowing of the Nile immediately followed. Thus it warned them, like a faithful 
dog, to escape from the region of the inundation. 

TELESCOPIC OBJECTS. 

1. a Canis Majoris — A brilliant star, with a distant companion; R. A. 7h. 30m. 55s. ; 
Dec. N. 5° 37' 8". A lj£, yellowish white; B 8, orange tinge. Several small stars in the 
field. 

2. (5 Canis Majoris— A star with a distant companion in the loins ; R. A. 7h. 01m. 53s. * 
Dec, S. 26° OS' 6". A 3%, light yellow ; B 7&, very pate. Other small stars in the field 
A line from Betelguese through Sirius intercepts it 12° below the latter star. 

3. e Canis Majoris (Adliara) — A star with a distant companion in the belly ; R. A 
6h. 52m. 20s. Dec. S. 28° 45' 5". A 2}£, pale orange : B 7, violet. Found by running a 
line from the middle of Orion's belt through /3 just west of Sirius, to about 14° beyond 
the latter star. 

4. A cluster in the back of the head ; R. A. 6h. 52m. 10s. ; Dec. S. 13° 29' 2". Tole- 
rably compressed ; stars of the 8th to 11th magnitudes, of which the four principal 
form the letter Y. 

5. A cluster between Sirius and Monoceros ; R. A. 7h. 10m. 35s. ; Dec. S. 15° 21' 4". 
Stars principally of the 10th magnitude. Discovered by Miss Herschel in 1785. 



CHAPTER V. 

CONSTELLATIONS ON THE MERIDIAN IN MARCH. 

AEGO NAVIS (the ship aego).— MAP III. 

113. This constellation occupies a large space in the southern 
hemisphere, though but a small part of it can be seen in the 
United States. It is situated S. E. of Canis Major, and may 
be known by the stars in the prow and deck of the ship. 

114. If a straight line joining Betelguese and Sirius, be pro- 
duced 18° to the southeast, it will point out JVaos, a star of the 
2d magnitude, in the rowlock of the ship. This star is in the 
S. E. corner of the Egyptian X, and of the large equilateral 
triangle made by itself with Sirius and the Dove. When on the 
meridian, it is seen from this latitude about 8° above the south- 

Telescopic Objects.-— Alpha ? Delta ? Epsilon ? What clusters ? 
113. Size and situation of Argo Navis? How known? 114. How find iVaos, and 
where situated ? How high when on the meridian ? 



ARGO NAVIS. 63 

era horizon. It conies to the meridian on the 3d of March, 
about half an hour after Procyon, and continues visible but a 
few hours. 

115. Gamma, in the middle of the ship, is a star of the 2d 
magnitude, about 1° S. of Xaos, and just skims above the south- 
ern horizon for a few minutes, and then sinks beneath it. The 
principal star in this constellation is called, after one of the 
pilots, Canopus; it is of the 1st magnitude, 36° nearly S. of 
Sirius, and comes to the meridian It minutes after it ; but hav- 
ing about 53° of S. declination, it cannot be seen in the United 
States. The same is true of Miaplacidus, a star of the 1st magni- 
tude in the oars of the ship, about 25° E. of Canopus, and 61° 
S. of Alphard, in the heart of Hydra. 

An observer in the northern hemisphere, can see the stars as many degrees south of 
the equinoctial In the southern hemisphere, as his own latitude lacks of 90°, and no 
more. 

116. Marked, is a star of the 4th magnitude, in the prow of 
the ship, and may be seen from this latitude 16° S. E. of Sirius, 
and about 10° E. of Wesen, in the back of the Dog. This star 
may be known by its forming a small triangle with two others 
of the same magnitude, situated a little above it, on the E., 3° 
and 4° apart. 

lit. This constellation contains 64 stars, of which two are 
of the 1st magnitude, four of the 2d, and nine of the 3d. Most 
of these are too low down to be seen in the United States. 

HISTORY. 

This constellation is intended to perpetuate the memory of the famous ship which car- 
ried Jason and his 54 companions to Colchis, when they resolved upon the perilous 
expedition of recovering the golden fleece. The derivation of the word Argo has been 
often disputed. Some derive it from Argos, supposing that this was the name of the 
person who first proposed the expedition, and built the ship. Others maintain that it 
was built at Argos, whence its name. Cicero calls it Argo, because it carried Grecians, 
commonly called Argives. Diodorus derives the word from dpybi, which signifies swift. 
Ptolemy says, but not truly, that Hercules built the ship, and called it Argo, after a son 
of Jason, who bore the same name. This sliip had fifty oars, and being thus propelled 
must have fallen far short of the bulk of the smallest ship craft used by moderns. It is 
even said that the crew were able to carry it on their backs from the Danube to the 
Adriatic. 

According to many authors, she had a beam on her prow, cut in the forest of Dodona 
by Minerva, which had the power of giving oracles to the Argonauts. This ship was the 
first, it is said, that ever ventured on the sea. After the expedition was finished, and 
Jason had returned in triumph, he ordered her to be drawn ashore at the isthmus of 
Corinth, and consecrated to Neptune, the god of the sea. 

Sir Isaac Newton endeavors to settle the period of this expedition at about 30 years 

115. Size and situation of Gamma? Name the principal star in this constellation? 
Its magnitude? Is it ever seen in the U. S. ? What said of Miaplacidus? Remark in 
fine print? 116. What said of Markeb ? How known? 117. Number of stars ia 
Argo Navis ? Magnitudes ? 

History. — Design of this constellation? Import of the term Argo f Size and struc- 
ture of the ship? What myth respecting this ship? What remark respecting Sir 
Isaac Newton? Dr. Bryant's opinion ? 



64 ASTRONOMY. 

before the destruction of Troy, and 43 years after the death of Solomon. Dr. Bryant 
however, rejects the history of the Argonautic expedition as a mere fiction of the Greeks, 
and supposes that this group of stars, which the poets denominate Argo Navis, refers to 
Noah's ark and the deluge, and that the fable of the Argonautic expedition is founded 
on cei *-ain Egyptian traditions that related to the preservation of Noah and his family 
during the flood. 

TELESCOPIC OBJECTS. 

1. i Argo Navis — A star with a distant companion ; R. A. 8h. 00m. 44s. ; Dec. S. 23° 
50' 8". A 3}£, pale yellow; B 10, greyish. Other small stars in the field. 

2. A small galaxy cluster ; R. A. 7h. 37m. 44s ; Dec. S. 23° 29' 1". 

3. A neat double star over the ship's stern ; R. A. 7h. 38m. 08s. ; Dec. S. 14° 18' 3°. 
A 7, silvery white ; B 73£, pale white. 

4. A close double star over the Argo's stern ; R. A. 7h. 40m. 27s. ; Dec. S. 11° 48' 3". 
A 7%, pale yellow ; B 9, light blue. 

5. A bright planetary nebula ; R. A. 7h. 34m. 46s. ; Dec. S. 17° 50' 2". A fine object, 
pale bluish white, and may be identified by several small stars in its vicinity. See Map 
VIII. , Fig. 37. 



CANCER (the crab).— MAP III. 

118. Cancer is now the fifth constellation and fourth sign of 
the Zodiac. It is situated in the ecliptic, between Leo on the 
E. and Gemini on the W. It contains 83 stars, of which one is 
of the 3d, and seven of the 4th magnitude. Some place the first- 
mentioned star in the same class with the other seven, and con- 
sider none larger than the 4th magnitude. 

119. Beta is a star of the 3d or 4th magnitude, in the south- 
western claw, 10° N. E. of Procyon, and may be known from 
the fact that it stands alone, or at least has no star of the same 
magnitude near it. It is midway between Procyon and Acubens. 

120. Acubens, is a star of similar brightness, in the south- 
eastern claw, 10° N. E. of Beta, and nearly in a straight line 
with it and Procyon. An imaginary line drawn from Capella 
through Pollux, will point out Acubens, at the distance of 24 p 
from Pollux. It may be otherwise distinguished by its standing 
between two very small stars close by it in the same claw. 

121. The southern Asellus, marked Delta, is situated in the 
line of the ecliptic, and, in connection with Wasat and Tejat, 
marks the course of the earth's orbit for a space of 36° from 
the solstitial colure. 

A few degrees S. of Cancer, and about 17° E. of Procyon, are four stars of the 4th 
magnitude, 3° or 4° apart, which mark the head of Hydra. The rest of this constellation 
is delineated on Map IV. 

Telescopic Objects. — Iota? What cluster? Double stars? Nebula? Point out on 
the map ? 

118. Place of Cancer in the Zodiac? In other respects? Number and size of its 
stars? 119. Beta? How known? 120. Acubens? How found? 121. Situation 
of Delta ? Remarks respecting Hydra ? Respecting the sign Cancer ? 



CANCER. 65 

The beginning of the sign Cancer (not the constellation) is called the Tropic of Can- 
cer, and when the sun arrives at this point, it has reached its utmost limit of north decli- 
nation, where it seems to remain stationary a few days before it begins to decline again 
to the south. This stationary attitude of the sun is called the summer solstice; from two 
Latin words signifying the sun's standing still. The distance from the first point of 
Cancer to the equinoctial, which, at present, is 23° 27%', is called the obliquity of the 
ecliptic. It is a remarkable and well ascertained fact, tlrat this is continually growing 
less and less. The tropics are slowly and steadily approaching the equinoctial, at the 
rate of about half a second every year ; so that the sun does not now come so far north 
of the equator in summer, nor decline so far south in winter, as it must have done at the 
creation, by nearly a degree. 

HISTORY. 

In the Zodiacs of Esne and Dendera, and in most of the astrological remains of Egypt, 
a Scarabseus, or Beetle, is used as the symbol of this sign ; but in Sir William Jones' 
Oriental Zodiac, and in some others found in India, we meet with the figure of a crab. 
As the Hindoos, in all probability, derived their knowledge of the stars from the Chal- 
deans, it is supposed that the figure of the crab, in this place, is more ancient than the 
Beetle. 

In some eastern representations of this sign, two animals, like asses, are found in this 
division of the Zodiac ; and as the Chaldaic name for the ass may be translated rnuddi- 
ness, it is supposed to allude to the discoloring of the Nile, which river was rising when 
the sun entered Cancer. The Greeks, in copying this sign, have placed two asses as the 
appropriate symbol of it, which still remain. They explain their reason, however, for 
adopting this figure, by saying that these are the animals that assisted Jupiter in his 
victory over the giants. 

Dopuis accounts for the origin of the asses in the following words : — " Le Cancer ou 
sont les etoiles appellees les anes, forme 1'empreinte du pavilion d' Issachar que Jacob 
assimile a Pane." 

Mythologists give different accounts of the origin of this constellation. The prevail- 
ing opinion is, that while Hercules was engaged in his famous contest with the dreadful 
Lernaean monster, Juno, envious of the fame of his achievements, sent a sea-crab to 
bite and annoy the hero's feet, but the crab being soon dispatched, the goddess, to reward 
its services, placed it among the constellations. 

" The Scorpion's claws here clasp a wide extent, 
And here the Crab's in lesser clasps are bent." 

TELESCOPIC OBJECTS. 

1. 6 Cancri — A very delicate double star, under the Crab's mouth ; B. A. 8h. 35m. 
85s. ; Dec. N. 18° 44' 04". A 4%, straw color ; B 15 blue, only seen by glimpses. 

2. e Cancri — A star with a distant companion, on the Crab's body ; R. A. 8h. 31m. 
16s.; Dec. N. 20° 06' 02". A 6%, and B 7, both pale white ; and a third star in the field 
of nearly the same magnitude. 

3. £- Cancri — A fine triple star, just below the after claws of the Crab ; R. A. 8h. 03m. 
02s.; Dec. N. 18° 07' 05". A 6, yellow; B 7, orange tinge; C 7%, yellowish. Supposed 
to be a Ternary system. 

4. About 7° northeasterly from Tegmine, is a nebulous cluster of very minute stars, in 
the crest of Cancer, sufficiently luminous to be seen by the naked eye. It is situated in 
a triangular position with regard to the head of the Twins and the Little Dog. It is about 
20° W. of each. It may otherwise be discovered by means of two conspicuous stars of 
the 4th magnitude, lying one on either side of it, at the distance of about 2°, called the 
northern and southern Aselli. By some of the Orientalists, this cluster was denominated 
Prcesepe, the Manger, a contrivance which their fancy filled up for the accommodation 
of the Aselli or Asses ; and it is so called by modern astronomers. The appearance of 
this group to the unassisted eye, is not unlike the nucleus of a comet, and it was repeat- 
edly mistaken for the comet of 1832, which, in the month of November, passed in its 
neighborhood. Map VLH., Fig. 38. 

5. A rich but loose cluster in the Crab's- southern claw, where a line from Rigel 
through Procyon, into the east-northeast, will find it about 5° north of e in the Hyades ; 
R. A. 8h. 42m. 26s. ; Dec. N. 12° 23' 06". Stars mostly of the 9th and 10th magnitudes. 
See Map VLU., Fig. 39. 

History.— What other figures for Cancer? Egyptian? Hindoo? Greek? Origin of 
this constellation ? 
Telescopic Objects.— Delta ? Epsilon ? Zeta ? What Clusters ? Point out on the Map 



66 ASTRONOMY. 

CHAPTER VI. 

CONSTELLATIONS ON THE MERIDIAN IN APRIL. 

LEO (the lion).— MAP IV. 

122. Leo is one of the most brilliant constellations in the 
winter hemisphere, and contains an unusual number of very 
bright stars. It is situated next E. of Cancer, and directly S. 
of Leo Minor and the Great Bear. 

The Hindoo astronomer, Varaha, says, " Certainly the southern solstice was once in 
the middle of Asleha {Leo) ; the northern in the first degree of Dhanishta" {Aquarius). 
Since that time, the solstitial, as well as the equinoctial points, have gone backward on 
the ecliptic 75°. This divided by 50 W gives 5373 years; which carry us back to the 
year of the world 464. Sir W. Jones says, that Varaha lived when the solstices were in 
the first degrees of Cancer and Capricorn ; or about 400 years before the Christian era. 

123. Leo is the fifth sign, and the sixth constellation of the 
Zodiac. The mean right ascension of this extensive group is 
150°, or 10 hours. Its center is therefore on the meridian the 
sixth of April. Its western outline, however, comes to the 
meridian on the 18th of March, while its eastern limit does not 
reach it before the 3d of May. 

This constellation contains 95 visible stars, of which one is 
of the 1st magnitude, one of the 2d, six of the 3d, and fifteen of 
the 4th. 

" One splendid star of highest dignity, 
One of the second class the Lion boasts, 
And justly figures the fierce summer's rage." 

124. The principal star in this constellation is of the 1st mag- 
nitude, situated in the breast of the animal, and named Regulus, 
from the illustrious Roman consul of that name. 

It is situated almost exactly in the ecliptic, and may be 
readily distinguished on account of its superior brilliancy. It is 
the largest and lowest of a group of five or six bright stars 
which form a figure somewhat resembling a sickle, in the neck 
and shoulder of the Lion. There is a little star of the 5th mag- 
nitude, about 2° S. of it, and one of the 3d magnitude 5° N. of 
it, which will serve to point it out. 

Great use is made of Regulus by nautical men, for determining their longitude at sea. 
Its latitude, or distance from the ecliptic, is less than j£°; but its declination, or dis- 
tance from the equinoctial, is nearly 13° N. ; so that its meridian altitude will be just 



122. Describe Leo. Its situation ? What remarkable statement of Varaha? Calcula- 
tions upon it? 123. Position of Leo in the Zodiac ? When on the meridian? Number 
and size of its stars ? 124. Its principal star? Situation? How distinguished? What 
use made of Regulus ? When on the meridian, where are Castor and Pollux ? 



LEO. 67 

equal to that of the sun on the 19th of August. Its right ascension is very nearly 150°. 
It therefore culminates about 9 o'clock on the 6th of April. 

When Regulus is on the meridian, Castor and Pollux are seen about 40° N. W. of it, 
and the two stars in the Little Dog are about the same distance in a S. W. direction ; 
with which, and the two former, it makes a large isosceles triangle whose vertex is at 
Regulus. 

125. The next considerable star is 5° X. of Regulus, marked 
Eta, situated in the collar ; it is of between the 3d and 4th 
magnitudes, and with Regulus constitutes the handle of the 
sickle. Those three or four stars of the 3d magnitude, N. and 
W. of Eta, arching round with the neck of the animal, describe 
the blade. 

126. Al Gieba is a bright star of the 2d magnitude, situated 
in the shoulder, 4° in a jST. E. direction from Eta, and may be 
easily distinguished by its being the brightest and middle one of 
the three stars lying irr a semicircular form curving toward the 
west ; and it is the first in the blade of the sickle. 

127. Adhafera is a star of the 3d magnitude, situated in the 
neck, 4° X. of Al Gieba, and may be known by a very minute 
star just below it. This is the second star in the blade of the 
sickle. 

128. Ras al Asad, situated before the ear, is a star of the 3d 
or 4th magnitude, 6° W. of Adhafera, and is the third in the 
blade of the sickle. The next star, Epsilon, of the same magni- 
tude, situated in the head, is 2J° S. W. of Ras al Asad, and a 
little within the curve of the sickle. About midway between 
these, and a little to the E., is a very small star hardly visible 
to the naked eye. 

129. Lambda, situated in the mouth, is a star of the 4th 
magnitude, 3^-° S. W. of Epsilon, and the last in the sickle's 
point. Kappa, situated in the nose, is another star of the same 
magnitude, and about as far from Lambda as Epsilon. Epsilon 
and Kappa are about 4J° apart, and form the longest side of a 
triangle, whose vertex is in Kappa. 

130. Zozma, situated in the Iback of the Lion, is a star of the 
3d magnitude 18° N. E. of Regulus, and midway between it and 
Coma Berenices, a fine cluster of small stars, 18° IS". E. of 
Zozma. 

131. Theta, situated in the thigh, is another star of the 3d 
magnitude, 5° directly S. of Zozma, and so nearly on the same- 
meridian that it culminates but one minute after it. This star 

125. Next principal star — size and position? 126. Al Gieba? How known? 

127. Adhafera? 123. Ras al Asad? Epsilon? 129. Situation and size of Lambda ? 

Of Kappa? 180. Of Zozma? 131. Of Theta? What triangle? What other stars 
mentioned? 



68 ASTRONOMY. 

makes a right-angled triangle with Zozma" on the N. and Dene- 
bola on the E., the right angle being at Theta. 

Nearly in a straight line with Zozma and Theta, and south 
of them, are three or four smaller stars, 4° or 5° apart, which 
mark one of the legs. 

132. Denebola is a bright star of the first magnitude, in the 
brush of the tail, 10° S. B. of Zozma, and may be distinguished 
by its great brilliancy. It*is 5° W. of the equinoctial colure, 
and comes to the meridian 1 hour and 41 minutes after Regulus, 
on the 3d of May ; when its meridian altitude is the same as 
the sun's at 12 o'clock the next day. 

When Denebola is on the meridian, Regulus is seen 25° W. of it, and Phad, in the 
square of Ursa Major, bears 39° N. of it. It forms, with these two, a large right-angled 
triangle ; the right angle being at Denebola. It is so nearly on the same meridian with 
Phad that it culminates only four minutes before it. 

Denebola is 3533" W. of Arcturus, and about the same distance N. W. of Spica Vir- 
ginis, and forms, with them, a large equilateral triangle on the S. E. It also forms with 
Arcturus and Cor Caroli a similar figure, nearly as large on the N. E. These two 
triangles, being joined at their base, constitute a perfect geometrical figure of the form 
of a Rhombus, called by some, the Diamond of Virgo. 

A line drawn from Denebola through Regulus, and continued 7° or 8° further in the 
same direction, will point out Xi and Omicron, of the 3d and 4th magnitudes, situated 
in the foreclaws, and about 3° apart. 

There are a number of other stars of the 3d and 4th magnitudes in this constellation, 
which require no description, as the scholar will easily trace them out from the map. 
The position of Regulus and Denebola are often referred to in the geography of the 
heavens, as they serve to point out other clusters in the same neighborhood. 

HISTORY. 

According to Greek fable, this Lion represents the formidable animal which infested 
the forests of Nemsea. It was slain by Hercules, and placed by Jupiter among the stars 
in commemoration of the dreadful conflict. Some writers have applied the story of the 
twelve labors of Hercules to the progress of the sun through the twelve signs of the 
ecliptic; and as the combat of that celebrated hero with the Lion was his first labor, 
they have placed Leo as the first sign. The figure of the Lion was, however, on the 
Egyptian charts long before the invention of the fables of Hercules. It would seem, 
moreover, according to the fable itself, that Hercules, who represented the sun, actually 
slew the Nemsean Lion, because Leo was already a zodiacal sign. 

In hieroglyphic al writing the Lion was an emblem of violence and fury; and the 
representation of this animal in the Zodiac, signified the intense heat occasioned by the 
sun when it entered that part of the ecliptic. The Egyptians were much annoyed by 
lions during the heat of summer, as they at that season left the desert, and haunted the 
banks of the Nile, which had then reached its greatest elevation. It was therefore 
natural for their astronomers to place the Lion where we find him in the Zodiac. 

The figure of Leo, very much as we now have it, is in all the Indian and Egyptian 
Zodiacs. The overflowing of the Nile, which was regularly and anxiously expected every 
year by the Egyptians, took place when the sun^was in this sign. They therefore paid 
more attention to it, it is to be presumed, than to any other. This was the principal 
reason, Mr. Green supposes, why Leo stands first in the zodiacs of Dendera. 

In the Hebrew Zodiac, Leo is assigned to Judah, on whose standard, according to all 
traditions, a Lion is painted. This is clearly intimated in numerous passages of the 
Hebrew writings : Ex. — " Judah is a Lion's whelp ; he stooped down, he couched as a 

132. Size and position of Denebola? How known ? When does it come to the meri- 
dian as compared with Regulu3 ? What said of its meridian altitude ? When on the 
meridian where is Regulus seen? Phad? What triangle? How is Denebolo situated 
with respect to Arcturus and Spica Virginis ? To Cor Caroli ? What other large figures ? 

History. — Greek fable? Egyptian? Hebrew Zodiacs? Scripture allusions to the 
Lion? 



LEO MINOR. 69 

Lion, and as an Old Lion ; who shall rouse him up?" Gen. xlix. 9. " The Lion of tie 
tribe of Judah hath prevailed." Rev. v. 5. 

TELESCOPIC OBJECTS 

1. a Leonis (Regulus)— A. bright star with a distant companion ; R. A. 9h. 59m. 51s. ; 
Dec. N. 12° 44 08". A 1, flushed white ; B 8%, pale purple. 

2 8 Leonis (Denebola) — A fine star with a distant companion ; R. A. llh. 40m. 54s. ; 
Dec. N. 15° 28' 0". A 2%, bluish; B 8, dull red. 

3. y Leonis (Al Gieba) — A splendid double star ; R. A. lOh. 11m. 0§s. ; Dec. N. 20* 
39' 0". A 2, bright orange; B 4, greenish yellow. A most beautiful object— binary- 
period supposed about 1000 years. Map VILL, Fig. 6. 

4. 5 Leonis (Zosma) — A coarse triple star ; R. A. llh. 05m. 35s. ; Dec. N. 21° 24* 1". 
A 3, pale yellow ; B 13, blue ; C 9, violet. 

5. e Leonis — A star with a distant companion in the mouth of Leo ; R. A. 9h. 30m. 46s. ; 
Dec. N. 24° 30' 5". A 3, yellow ; B 10, pale grey. 

6. c Leonis— A binary star in the flank, 7° S. W. of Denebola (F on map) ; R. A. llh. 
15m. 35s. ; Dec. N. 11° 24' S". It forms a neat scalene triangle with 8 and ■&. A 4, pale 
yellow ; B 7% , light blue ; a beautiful object. 

7. /j, Leonis (Bas AlAsad)—A double star; R. A. 9h. 43m. 39s. ; Dec. N. 26° 46' 5*. 
A 3, orange ; B 10, pale lilac. 

8. A neat double star near Zozma ; R. A. llh. 05m. 17s. ; Dec. 21° 00' 3". Components 
both 7%, and both faint yellow; a beautiful object. 

9. A bright nebula near the hind paws ; R. A. lOh. 57m. 37s. ; Dec. N. 0° 49' 6". Large, 
elongated, well-defined — an enormous mass of luminous matter — one of a vast number 
of spherical nebulae in the vicinity. 

10. A bicentral white nebula in the lower jaw, 2° south of 1 Leonis ; R. A. 9h. 23m. 
07s. ; Dec. N. 22° 1 2' 1". May be classed as double — small stars in field ; difficult object. 
See Map VIII., Fig. 40. 

11. A lucid white nebula on the Lion's ribs, about 9° due east of Regulus ; R. A. lOh. 
35m. 31s. ; Dec. N. 12° 31' 9". Round and bright, with two small stars in field. Another 
large pale white nebula, about 1° east of it. 

12. A pair of bright class nebula in the Lion's belly ; R. A. lOh. 39m. 49s. ; Dec. N. 
13° 28'. Found south of line joining Regulus and "& Leonis, about 10° east of, and 
nearly on a parallel with the latter. 

13. A large, elongated nebula, with a bright nucleus on the Lion's haunch ; R. A. 
llh. 11m. 48s. ; Dec. N. 13° 52' 4" ; just 3° southeast of #, with another smaller nebula, 
and several stars in the field. Map VLU., Fig. 41. 

LEO MINOR (the little lion).— MAP IV. 

133. Leo Minor contains 53 stars, including only one of the 
3d magnitude, and five of the 4th. The principal star is situated 
in the body of the animal, 13° 1ST. of Gamma Leonis, in a straight 
line with Phad, and may be known by a group of smaller stars, 
a little above it on the IS". W. 

It forms an equilateral triangle with Gamma and Delta Leonis, the vertex being in 
Leo Minor. This star is marked with the letter I, in modern catalogues, and being the 
principal representative of the constellation, is itself sometimes called the Little Lion : 
8° E. of this star (the Little Lion) are two stars of the 4th magnitude, in the last paw 
of Ursa Major, and about 10° N. W. of it are two other stars of the 3d magnitude, in the 
first hind paw. 

" The Smaller Lion now succeeds ; a cohort 
Of fifty stars attend his steps ; 
And three, to sight unarm'd, invisible." 

Telescopic Objects. — Alpha? Beta? Gamma? Point out on the map. Delta? 
Epsilon? Iota? Mu?' What nebulae? Which shown on the map ? Point out. 
133. Describe Leo Minor ? Its principal star ? Helps form what triangle ? 



7 ASTRONOMY. 



134. This constellation was formed by Hevelius, out of the 
&lrffa!S informes, or unformed stars of the ancients, which lay 
scattered between the Zodiacal constellation Leo on the S and 

Swl ? 01 ; ?? th ? N - l tS - mean ri - ht as ^nsion is the "same 
with that of Regulus, and it comes to the meridian at the same 
time on the 6th of April. 

TELESCOPIC OBJECTS. 

42m^ HT SIc L N E IIo L 00^» We ?, n **"«* Ca P?^ but given to Leo Minor; R. A. 8h. 
tan. 44s. , Deo. N. 34 00 6 . Direct telescope 16° north by east of Presepe in Cancer? 



SEXTAN'S (the sextant). — MAP IV. 

135. Sextans contains 41 very small stars, including only one 
as large as the 4th magnitude. This is situated very near the 
equinoctial, 13° S of Regulus, and comes to the meridian about 
the same time on the 6th of April. The other stars in this con- 
stelJation are too small to engage attention. A few of the 
largest of them may be traced out from the map 

mrnmrnmsmm 



stars. 



telescopic objects. 

9hhsL D °£ ™ Dec N % e Il?V f °Tt e !? g ° f ^ th ° Ugh C1 ' lmped into the sex ^ nt I *• A 

the^tari 1 ? 111 of ^ecXinX? MeanTXT^at remark ^p^h^he^^^f 
Telescopic Objects.— What nebula ? Situation ? How find ? 

JZTeSZs'tlS-^ ***>*<**" » ™*> -bulaf What remarkable a*h. 



HYDRA. 71 

2. A neat double star on the north extreme of the graduated limb of the instrument; 
and three-fifths of the distance between Alphard and Denebola ; R. A. lOh. 35m. 02s. ; 
Dec. N. 5° 35' 2". A 7, topaz yellow; B 8, smalt blue ; a fine object. 

3. A. bright class round nebula on the frame of the instrument ; R. A. lOh. 05m. 58s. ; 
Dec. N. 4° 15' 1". A good telescope shows another large but faint nebula near by. 

This object is on or near the spot where the Capuchin, De Rheita, fancied he saw the 
napkin of St. Veronica, in 1783. Captain Smyth has a picture of this wonderful napkin ; 
and Sir J. Herschel remarks that " many strange things were seen among the stars 
before the use of powerful telescopes became common." 



HYDRA AND THE CUP.— MAP IY. 

136. Hydra, {the Water- Serpent,) is an extensive constella- 
tion, winding from E. to W. in a serpentine direction, over a 
space of more than 100 degrees in length. It lies south of 
Cancer, Leo and Yirgo, and reaches almost from Canis Minor 
to Libra. It contains sixty stars, including one of the 2d mag- 
nitude, three of the 3d, and twelve of the 4th. 

137. Alphard or Cor Hydrce, in the heart, is a lone star of 
the 2d magnitude, 23° S. S. W. of Regulus, and comes to the 
meridian at the same time with Lambda, in the point of the 
sickle, about 20 minutes before 9 o'clock on the 1st of April. 
There is no other considerable star near it, for which it can be 
mistaken. An imaginary line drawn from Gamma Leonis 
through Regulus, will point out Cor Hydrse, at the distance 
of 23°. 

138. The head of Hydra may be distinguished by means of 
four stars of the 4th magnitude, 2-J-° and 4° apart, situated 6° 
S. of Acubens, and forming a rhomboidal figure. The three 
upper stars in this cluster form a small arch, and may be known 
by two very small stars just below the middle one, making with 
it a very small triangle. The three western stars in the head 
also make a beautiful little triangle. The eastern star in this 
group, marked Zeta, is about 6° directly S. of Acubens, and 
culminates at the same time. 

139. When Alphard is on the meridian, Alices, of the 4th mag- 
nitude, situated in the bottom of the Cup, may be seen, 24° S. E. 
of it, and is distinguished by its forming an equilateral triangle 
with Beta and Gamma, stars of the same magnitude, 6° S. and 
E. of- it. Alkes is common both to Hydra and the Cup. Beta, 
on the S., is in Hydra, and Gamma, on the IS". E., is near the 
middle of the Cup. A line drawn from Zozma, through Theta 

136. Describe Hydra? Its situation ? Number and magnitude of its stars? 137. Po- 
sition and magnitude of Alphard ? How pointed out ? 138. How is the head of Hydra 
distinguished? 139. What said of Alkes? Of Beta and Gamma? How is Beta 
found? 



72 ASTRONOMY. 

Leonis, and continued 38^-° directly S. will reach Beta ; it is 
therefore on the same meridian, and will culminate at the same 
time on the 23d of April. 

140. The Cup itself (called also the Crater), may be easily 
distinguished by means of six stars of the 4th magnitude, form- 
ing a beautiful crescent, or semicircle , opening to the W. The 
center of this group is about 15° below the equinoctial, and 
directly S. of the hinder feet of Leo. The crescent form of the 
stars in the Cup is so striking and well defined, when the moon 
is absent, that no other description is necessary to point them 
out. Its center comes to the meridian about two hours after 
Alphard, on the same evening ; and consequently, it culminates 
at 9 o'clock, one month after Alphard does. The remainder of 
the stars in this constellation may be easily traced by aid of 
the map. 

141. When the head of Hydra is on the meridian, its other 
extremity is many degrees below the horizon, so that its whole 
length cannot be traced out in the heavens until its center, or 
the Cup, is on the meridian. 



-" Near the equator rolls 



The sparkling Hydra, proudly eminent 
To drink the Galaxy's refulgent sea ; 
Nearly a fourth of the encircling curve 
Which girds the ecliptic, his vast folds involve - ; 
Yet ten the number of his stars diffused 
O'er the long track of his enormous spires ; 
Chief Yearns his heart, sure of the second rank, 
But emulous to gain the first." — Eudosia. 

HISTORY. 

The astrologers of the east, in dividing the celestial hosts into various compartments, 
assigned a popular and allegorical meaning to each. Thus the sign Leo, which passes 
the meridian about midnight, when the sun is in Pisces, was called the House of the 
Lions, Leo being the domicil of Sol. 

The introduction of two serpents into the constellations of the ancients, had its origin, 
it is supposed, in the circumstances that the polar one represented the oblique course of 
the stars, while the Hydra, or Great Snake, in the southern hemisphere, symbolized the 
moon's course ; hence the Nodes are called the Dragon's head and tail to this day. 

The hydra was a terrible monster, which, according to mythologists, infested the 
neighborhood of the lake Lerna, in the Peloponnesus. It had a hundred heads, accord- 
ing to Diodorous ; fifty, according to Simonides ; and nine, according to the more com- 
monly received opinion of Apollodorus, Hyginus, and others. As soon as one of these 
heads was cut off, two immediately grew up if the wound was not stopped by fire. 

" Art thou proportion'd to the hydra's length, 
Who by his wounds received augmented strength? 
He raised a hundred hissing heads in air, 
When one I lopp'd, up sprang a dreadful pair." 

To destroy this dreadful monster, was one of the labors of Hercules, and this he easily 
effected with the assistance of Iolaus, who applied a burning iron to the wounds as 
soon as one head was cut off. While Hercules was destroying the hydra, Juno, jealous of 
his glory, sent a sea-crab to bite his foot. This new enemy was soon despatched ; and 

140. How is the Cup distinguished ? Is it easily found ? 141. What is said of the 
extent of Hydra east and west? History of Hydra ? 



URSA MAJOR. 73 

Juno was unable to succeed in her attempts to lessen the fame of Hercules. The con- 
queror dipped his arrows in the gall of the Hydra, which ever after rendered the wounds 
inflicted with them incurable and mortal. 

This fable of the many-headed hydra may be understood to mean nothing more than 
that the marshes of Lerna were infested with a multitude of serpents, which seemed to 
multiply as fast as they were destroyed. 

TELESCOPIC OBJECTS. 

1 a ©rateris — A star with two very distant companions in the base of the cup ; R. A. 
iOh'. 52m. 00s ; Dec. S. 17° 26' 9'. A. 4, orange tint; B 8, intense blood color ; C 9, pale 
blue. 

2. y Crateris — A close double star, in the center of the cup ; R. A. llh. 16m. 54s. ; 
Dec. S. 16 3 48' 3"; A 4, bright white ; B 14, grey; with a star of the 11th magnitude fol- 
lowing, on a line with A. B. 25' distant. 

3. 6 Crateris — A star with a very distant companion, on the cup, midway between 
Alphard and Spica, but a little south of the line joining them; R. A. llh. 11m. 21s.; 
Dec. S. 13° 54' S". A S%, pale orange ; B 11, pale blue— other small stars in the field. 

4. a HYDR.E (Cor Eydroz)—h. bright star in the heart of Hydra with a distant com- 
panion ; R. A. lh. 19m. 44s. ; Dec. S. 7° 58' 1°. A 2, orange tint ; B 10, pale green. 

5. (5 Hydr,£ — A star with a distant companion in the head of Hydra ; R. A. 8h. 29m. 
14s. ; Dec. N. 6° 15' 5°. A 4, light topaz ; B 9, livid— several other stars in the field. 

6. £ Htdr^:— A double star in the head; R. A. 8h. 38m. 18s.; Dec. N. 7° 00' 2". A 4, 
pale yellow; B 8}£, purple. 

7. A planetary nebula in the middle of the body; R. A. lOh. 17m. 01s.; Dec. S. 17' 
50' 6"; greyish white. 



CHAPTER VII. 

CONSTELLATIONS ON THE MERIDIAN IN MAY. 

URSA MAJOR (the great beae).— MAPS IV. AKD VI. 

142. Ursa Major is situated between Ursa Minor on the north, 
and Leo Minor on the south. It is one of the most noted and 
conspicuous in the northern hemisphere. It has been an object 
of universal observation in all ages of the world. 

The priests of Belus and the Magi of Persia, the shepherds of Chaldea, and the Phoe- 
nician navigators, seem to have been equally struck with its peculiar outlines. And it 
is somewhat remarkable, that a remote nation of American Aborigines, the Iroquois, 
and the earliest Arabs of Asia, should have given to the very same constellation the 
name of " Great Bear," when there had probably never been any communication 
between them; and when the name itself is so perfectly arbitrary, there being no resem- 
blance whatever to a bear, or to any other animal. 

143. It is readily distinguished from all others by means of a 
remarkable cluster of seven bright stars, forming what is fami- 
liarly termed the Dipper, or Ladle. In some parts of England 
it is called " Charles' Wain," or wagon, from its fancied resem- 



Telescopio Objects.— Alpha ? Gamma? Delta? Alpha Hydrae? Delta Hydrae? 
Eta Hydrae ? What- Nebula ? 

142. Describe Ursa Major? What remarkable fact as to its name? 143. How dis- 
tinguished ? What other names for the Dipper ? What remark in small type ? 





74 ASTRONOMY. 

blance to a wagon drawn by three horses in a line. Others call 
it the Plough. The cluster, however, is more frequently put for 
the whole constellation, and called simply the Great Bear. 

We see no reason to reject the very appropriate appellation of the shepherds, for the 
resemblance is certainly in favor of the Dipper; the four stars in the square forming the 
bowl, and the other three the handle. 

144. When the Dipper is on the meridian, above the pole, the 
bottom lies toward us, with the handle on the right. 

Benetnasch is a bright star of the 2d magnitude, and is the 
first in the handle. The second, or middle star in the handle is 
Mizar, T° distant from Benetnasch. It may be known by means 
of a very minute star almost touching it, called Alcor. 

145. The third star in the handle is called Alioth, and is ab^out 
4-|- W. of Mizar. Alioth is very nearly opposite Shedir in Cas- 
siopeia, and at an equal distance from the pole. Benetnasch, 
Mizar, and Alioth constitute the handle, while the next four in 
the square form the bowl of the Dipper. 

146. Five and a half degrees W. of Alioth is the first star in 
the top of the Dipper, at the junction of the handle, called 
Megrez ; it is the smallest and middle one of the cluster, and is 
used in various observations both on sea and land for important 
purposes. 

When Megrez and Caph have the same altitude, and are seen in the same horizontal 
line east and west, the polar star is then at its greatest elongation from the true pole of 
the heavens ; and this is the proper time for an observer to take its angle of elevation, 
in order to determine the latitude, and its azimuth or angle of declination, in order to 
determine the magnetic variation. 

14?. At the distance of 4^° S. W. of Megrez is Pkad, the 
first star in that part of the bottom which is next the handle. 

The stars in this cluster are so well known, and may be so easily described without 
reference to their relative bearings, that they would rather confuse than assist the 
student, were they given with ever so much accuracy. The several bearings for this 
cluster were taken when Megrez was on the meridian, and will not apply at any other 
time, though their respective distances will remain the same. 

148. At the distance of 8° W. of Phad, is the westernmost 
star in the bottom of the Dipper called Merak. The bright star 
5° N. of it, toward the pole, is called Dubhe. These two, are, 
by common consent, called the Pointers, because they always 
point toward the pole ; for, let the line which joins them be con- 
tinued in the same direction 28f° further, it will just reach the 
north pole. 

The names, positions, and relative distances of the stars in this cluster should be well 

144. How is the handle of the Dipper situated, when the Dipper is above the pole ? 
Describe Benetnasch? Mizar? How known? 145. Alioth? Megrez? Remark 

respecting? Phad? Remark in small print? 148. Merak and Dubhe? Constitute 
what? Remark respecting the names, positions and distances of the stars in Ursa 
Major? Why should these distances be well understood? 



URSA MAJOR. 75 

remembered, as they will be frequently adverted to. The distance of Dubhe, or the 
Pointer nearest to the north pole, is 2894°. The distance between the two upper stars in 
the Dipper is 10°; between the two lower ones is 8°; the distance from the brim to the 
bottom next the handle, is 4%°; between Megrez and Alioth, is 5%° ; between Alioth 
and Mizar, 4%°; and between Mizar and Benetnasch, 7°. 

The reason why it is important to have these distances clearly settled in the mind is, 
that these stars, being always in view, and more familiar than any other, the student 
will never fail to have a standard measure before him, which the eye can easily make 
use of in determining the distances between other stars. 

149. The position of Megrez in Ursa Major, and of Caph in 
Cassiopeia, is somewhat remarkable. They are both in the equi- 
noctial colure, almost exactly opposite each other, and equally 
distant from the pole. Caph is in the colure, which passes 
through the vernal equinox, and Megrez is in that which passes 
through the autumnal equinox. The latter passes the meridian 
at 9 o'clock, on the 10th of May, and the former just six months 
afterward, at the same hour, on the 10th of November. 

150. Psi, in the left leg of Ursa Major, is a star of the 4th 
magnitude, in a line with Megrez and Phad, distant from the 
latter 12-§-°. A little out of the same line, 3° farther, is another 
star of the 4th magnitude, marked JEpsilon, which may be dis- 
tinguished from Psi, from its forming a straight line with the two 
Pointers. 

151. The right fore-paw, and the two hinder ones, each about 
15° from the other, are severally distinguished by two stars of 
the 4th magnitude, between 1° and 2° apart. These three 
duplicate stars are nearly in a right line, 20° S. of, and in a 
direction nearly parallel with Phad and Dubhe, and are the only 
stars in this constellation that ever set in this latitude. 

There are a few other stars of equal brightness with those just described, but amidst 
the more splendid and interesting group with which they are clustered, they seldom 
engage our observation. 

The whole number of visible stars in this constellation is 87 ; of which five are of the 
2d, two of the 3d, and about twice as many of the 4th magnitude. 

HISTORY. 

Ursa Major is said to be Calisto, or Helice, daughter of Lycaon, king of Arcadia. She 
was an attendant of Diana, and mother of Areas, by Jupiter, who placed her among the 
constellations, after the jealousy of Juno had changed her into a bear. 

" This said, her hand within her hair she wound, 
Swung her to earth, and dragg'd her on the ground ; 
The prostrate wretch lifts up her hand in prayer; 
Her arms grow shaggy, and deform'd with hair, 
Her nails are sharpen'd into pointed claws, 
Her hands bear half her weight, and turn to paws ; 
Her lips, that once could tempt a god, begin 
To grow distorted in an ugly grin ; 

149. What said of Megrez and Caph? 150. Of Psi and Epsilon? 151. How find 
the feet of the figure? Number of stars in Ursa Major? Magnitudes? 

History. — Who was Ursa Major before she became a bear? What other supposition? 
How are the two bears represented by the Egyptians? What further remarks? 

B.G. 4 



76 ASTRONOMY. 

And lest the supplicating brute might reach 
The ears of Jove, she was deprived of speech. 
******* 

How did she fear to lodge in woods alone, 

And haunt the fields and meadows, once her own ! 

How often would the deep-mouth'd dogs pursue, 

Whilst from her hounds the frighted hunters flew." — Ovid's Met. 

Some suppose that her son Areas, otherwise called Bootes, was changed into Ursa 
Minor, or the Little Bear. It is well known, that the ancients represented both these 
constellations under the figure of a wagon drawn by a team of horses ; hence the appel- 
lation of Charles 1 Wain, or wagon. This is alluded to in the Phenomena of Aratus, a 
Greek poem, from which St. Paul quotes in his address to the Athenians : — 
" The one call'd Helix, soon as day retires, 

Observed with ease lights up his radiant fires . 

Ihe other, smaller, and with feebler beams, 

In a less circle drives its laay teams ; 

But more adapted for the sailor's guide, 

Whene'er, by night, he tempts the briny tide." 

In the Egyptian planispheres of remote antiquity, these two constellations are repre- 
sented by the figures of bears, instead of wagons; and the Greeks,who derived most of their 
astronomical symbols from the Egyptians, though they usually altered them to emblems 
of their own history or superstition, have, nevertheless, retained the original form of 
the two bears, It is said by Aratus, that the Phoenician navigators made use of Ursa 
Minor in directing their voyages : — 

" Observing this, Phoenicians plough the main :" 

while the Greeks confined their observations to Ursa Major. 

Some imagine that the ancient Egyptians arranged the stars near the North Pole, 
within the outlines of a bear, because the polar regions are the haunts of this animal, 
and also because it makes neither extensive journeys nor rapid marches. 

At what period men began to sail by the stars, or who were the first people that did 
bo, is not clear ; but the honor is usually given to the Phoenicians. That it was prac- 
ticed by the Greeks, as early as the time of the Trojan war, that is, about 1200 years 
B. C, we learn from Homer ; for he says of Ulysses, when sailing on his raft, that 

" Placed at the helm he sate, and mark'd the skies, 
Nor closed in sleep his ever watchful eyes." 

It is rational to suppose that the stars were first used as a guide to travellers by land, 
for we can scarcely imagine that men would venture themselves upon the sea by night, 
before they had first learned some safe and sure method of directing their course by 
land. And we find, according to Diodorus Siculus, that travellers in the sandy plains of 
Arabia were accustomed to direct their course by the Bears. 

That people travelled in these vast deserts at night by observing the stars, is directly 
proved by this passage of the Koran : — " God has given you the stars, to be guided in 
the dark, both by land and by sea." 

TELESCOPIC OBJECTS. 

1. a Ursa Majoris (I>ubhe, one of the pointers} — A fine star with a distant compa- 
nion ; R. A. lOh. 53m. 48s. ; Dec. N. 62° 36' 8". A 1 %, yellow ; B 8, yellow. 

2. /? Ursa Majoris (Jferak) — A bright star with a distant companion ; R. A. lOh. 52m. 
OS"; Dec. N. 57° 14' 2". A 2, greenish white ; B 11, pale grey — other stars in field. 

3. y Ursa Majoris (Phad) — A star with a distant companion ; R. A. llh. 45m. 23s. ; 
Dec. N. 54° 35' 1". A 2, topaz yellow ; B 9, ashy paleness, with a fine group of stars in 
the field. 

4. 6 Ursa Majoris (Megrez) — A fine star, suspected of variability, with a distant com- 
panion; R. A. 12h. 07m. 28s.; Dec. N. 57° 55' 3'. A 3, pale yellow; B 9, ash colored, 
with other stars in field. 

5. C, Ursa Majoris (31izar.) — A splendid double star in the middle of the tail ; R. A. 
13h. 17m. 28s. ; Dec. N. 55° 45' 8". A 3, brilliant white ; B 5, pale emerald. Alcor and 
other stars in the field. Map VHI. Fig. 7. 

Telescopic Objects.— Alpha ? Beta? Gamma? Delta? Zeta? Eta? Iota? No 
What nebula? Which shown on the map ? 



COMA BERENICES. 77 

6. 77 Ursa Majoris (Benebnasch) — A double star in the tip of the tail ; R. A. 13h. 41m. 
14s. ; Dec. N. 50° 06' 5". A 2}£, brilliant white ; B 9, dusky. 

7. 1 Ursa Majoris (Al Kaphrah) — A double star in the right fore paw ; R. A. 8h. 48m. 
14s. ; Dec. N. 48° 39' 9". A 3%, topaz yellow ; B 13, purple. Sir J. Ilerschel supposed A 
might be a satellite, shining only by reflection. 

8. V Ursa Majoris — A delicate double star in the left hind foot, just above £ or 
El Acola ; R. A. llh. 09m. 49s. ; Dec. N. 30° 58' 0'. A 4, orange tint ; B 12, cornelian blue ; 
a close but elegant object. 

9. A beautiful planetary nebula, just south of 0; R. A. lOh. 28m. 45s.; Dec. N. 54° 
20' 4". A small, well defined object, bluish white, and brightens towards the center. 

10. A bright nebula in the right fore leg; R. A. 9h. 10m. 54s.; Dec. N. 51° 40' 5". Of a 
pale creamy whiteness, with several bright stars in the northern part of the field. 
Nebula large, elliptical and nucleated. 

11. A bright-class round nebula above the Bear's ear ; R. A. 9h. 34m. 32s. ; Dec. N. 73" 
01' 2". Several stars in field, of 9th to 12th magnitude. 

12. A fine oval nebula in the ear ; R. A. 9h. 42m. 10s. ; Dec. N. 69° 51' 8*. 

13. A large milk-white nebula on the body, about 1° south of /3 or Merak ; R A. lln. 
02m. 02s. ; Dec. N. 56° 31' S\ 

14. A large planetary nebula on the flank, with several stars in the field, one of 
which is pretty close ; R. A. llh. 05m. 24s. ; Dec. N. 55° 52' 9'- About 2° to the S. E. of 
ft, and just south of a line from /? to y; a singular object, circular, uniform, and seem- 
ingly of the size of Jupiter. W. Ilerschel assigned this object to the 980th order of dis- 
tance. Map YHI., Fig. 42. 

15. A bright-class nebula in a poor field, behind the left hind leg, one-third the dis- 
tance from 6 towards Denebola ; R. A. llh. 5Sm. 51s. ; Dec. N. 43° 57' 3'. Of a lucid 
white, various and elongated. Map VUUL., Fig. 43. 

16. A large white nebula near the haunches ; R. A. 12h. 11m. 04s. ; Dec. N. 4S° 11' 1". 
A noble-sized oval, with a bright nucleus, the lateral edges better defined than the ends] 
Found by running a diagonal line across the square, from a through y, and about 7J£* 
beyond, into the S. E. 



COILA BERENICES (bEeenice's haie).— MAP IV. 

152. This is a beautiful cluster of small stars, situated about 
5° E. of trie equinoctial colure, and midway between Cor Caroli 
on the northeast, and Denebola on the southwest. If a straight 
line be drawn from Benetnasch through Cor Caroli, and pro- 
duced to Denebola, it will pass through it. 

153. The principal stars are of between the 4th and 5th mag- 
nitudes. According to Flamsted, there are thirteen of the 4th 
magnitude, and according to others there are seven ; but the 
student will find agreeably to his map, that there is apparently 
but one star in this group, entitled to that rank, and this is 
situated about 7° S. E. of the main cluster. 

Although it is not easy to mistake this group for any other in the same region of the 
skies, yet the stars which compose it are all so small as to be rarely distinguished in the 
full presence of the moon. The confused lustre of this assemblage of small stars some- 
what resembles that of the Milky Way. 

152. Describe Coma Berenices ? How find it ? 153. Its principal stars, their number 
Ac. ? What remark in fine print ? 



78 ASTRONOMY. 

154. The whole number of stars in this constellation is 43 ; 
its mean right ascension is 185°. It consequently is on the 
meridian the 13th of May. 

" Now behold 

The glittering maze of Berenice's Hair; 
Forty the stars ; but such as seem to kiss 
The flowing tresses with a lambent fire, 
Four to the telescope alone are seen." 

HISTORY. 

Berenice was of royal descent, and a lady of great beauty, who married Ptolemy Soter, 
or Evergetes, one of the kings of Egypt, her own brother, whom she loved with much 
tenderness. When he was going on a dangveous expedition against the Assyrians, she 
vowed to dedicate her hair to the goddess of beauty, if he returned in safety. Some 
time after the victorious return of her husband, Evergetes, the locks, which, agreeably 
to her oath, she had deposited in the temple of Venus, disappeared. The king expressed 
great regret at the loss of what he so much prized ; whereupon Conon, his astronomer, 
publicly reported that Jupiter had taken away the queen's locks from the temple and 
placed them among the stars. 

" There Berenice's locks first rose so bright, 
The heavens bespangling with dishevelled light." 
Conon being sent for by the king, pointed out this constellation, saying, " There behold 
the locks of the queen." This group being among the unformed stars until that time, 
and not known as a constellation, the king was satisfied with the declaration of the 
astronomer, and the queen became reconciled to the partiality of the gods. 

Callimachus, a historian and poet, who flourished long before the Christian era, has 
these lines as translated by Tytler : — 

" Immortal Conon, blest with skill divine, 
Amid the sacred skies behold me shine : 
E'en me, the beauteous hair, that lately shed 
Refulgent beams from Berenice's head ; 
The lock she fondly vowed with lifted arms, 
Imploring all the powers to save from harms 
Her dearer lord, when from his bride he flew, 
To wreak stern vengeance on the Assyrian crew." 

TELESCOPIC OBJECTS. 

1. A triple star, between the tresses and Virgo's northern wing ; R. A. 12h. 45m. 25s. , 
Dec. N. 22° 07' 0". A 5, pale yellow; B, indistinct; C 10, cobalt blue. About 7° south- 
east of a Berenices, and 20° west of Arcturus. 

2. A globular cluster, between the tresses and the Virgin's left hand, with a coarse 
pair and one single star in the field ; R. A. llh. 05m. 03s. ; Dec. N. 19° 01' 3". A brilliant 
mass of minute stars from the 11th to the 15th May ; compressed at center. A line 
through 6 and e Virginis, northward, meeting another from Arcturus over V Bootes, falls 
upon this magnificent object. 

3. A conspicuous nebula between the tresses and the virgin's left arm; R. A. 12h. 
48m. 52s. ; Dec. N. 22° 33' 2". A magnificent object, both in size and brightness, with 
several small stars in the field. Elongated, compressed in the centre, and was likened 
by Sir Charles Blagdon to a " Hack eye: 1 Map VIII., Fig. 44. 



COEYUS (the grow).— MAP IY. 

155. This small constellation is situated on the eastern part 
of Hydra, 15° E of the Cup, and is on the same meridian with 

154. What number of stars? 

History. — Who was Berenice? Story of the loss of her hair, <fec? 

Telescopic Objects.— What triple stars ? Cluster? Nebula? Point out on the Map. 

155. Where is Corvua situated ? Number of visible stars ? 



corvcjs. 79 

Coma Berenices, but as far S. of the equinoctial as Coma Bere- 
nices is N. of it. It therefore culminates at the same time, on 
the 12th of May. It contains nine visible stars, including three 
of the 3d magnitude, and two of the 4th. 

156. This constellation is readily distinguished by means of 
three stars of the 3d magnitude and one of the 4th, forming a 
trapezium or irregular square, the two upper ones being about 
3^-° apart, and the two lower ones 6° apart. 

15*7. The brightest of the two upper stars, on the left, is 
called Algorab, and is situated in the E. wing of the Crow ; it 
has nearly the same declination S. that the Dog Star has, and 
is on the meridian about the 13th of May. It is 21-J E. of 
Alkes in the Cup, 14^-° S. W. of Spica Virginis, a brilliant star 
of the 1st magnitude, to be described in the next chapter. 

158. Beta, on the back of Hydra, and in the foot of the Crow, 
is a star of the 3d magnitude, nearly 1° S. of Algorab. It is 
the brightest of the two lower stars, and on the left. The right- 
hand lower one is a star of the 4th magnitude, situated in the 
neck, marked Epsilon, about 6° W. of Beta, and may be known 
by a star of the same magnitude situated 2° below it, in the eye, 
and called Al Child. Epsilon is 21|° S. of the vernal equinox, 
and if a meridian should be drawn from the pole through 
Megrez, and produced to Epsilon Corvi, it would mark the equi- 
noctial colure. 

159. Gamma, in the W. wing, is a star of the 3d magnitude, 
3|- W. of Algorab, and is the upper right-hand one in the 
square. It is but 1° E. of the equinoctial colure. 

10 9 E. of Beta is a star of the 3d magnitude, in the tail of 
Hydra, marked Gamma ; these two, with Algorab, form nearly 
a right-angled triangle, the right angle being at Beta. 

HISTORY. 

The Crow, it is said, was once of the purest white, but was changed for tale-bearing to 
its present color. A fit punishment for such a fault. 

" The raven once in snowy plumes was drest, 
White as the whitest dove's unsullied breast, 
Fair as the guardian of the capitol, 
Soft as the Swan ; a large and lovely fowl ; 
His tongue, his prating tongue, had changed him quite, 
To sooty blackness from the purest white." 
According to Greek fable the Crow was made a constellation by Apollo. This god 
being jealous of Coronis (whom he tenderly loved), the daughter of Phlegyas and 



156. How is it found? 157. What said of Algorab ? 158. Of Beta? Epsilon? 
Al Chiba? What said of the Pole, Megrez, and Epsilon? 159. Of Gamma? What 
triangle ? 

History. — Story of the original color of Corvus ? Greek fable of the origin of the 
constellation ? What other account ? 



80 ASTRONOMY. 

mother of JSsculapius, sent a crow to watch her behavior; the bird perceived her cri- 
minal partiality for Ischys the Thessalian, and immediately acquainted Apollo with her 
conduct, which so fired his indignation that he lodged an arrow in her breast, and killed 
her instantly. 

" The god was wroth ; the color left his look, 

The wreath his head, the harp his hand forsook: 

The silver bow and feathered shafts he took, 

And lodged an arrow in the tender breast, 

That had so often to his own been prest." 
To reward the crow, he placed her among the constellations. 

Others say that this constellation takes its name from the daughter of Coronaeus, 
king of Phocis, who was transformed into a crow by Minerva, to rescue the maid from 
the pursuit of Neptune. The following, from an eminent Latin poet of the Augustan 
age, is her own account of the metamorphosis as translated into English verse by Mr. 
Addison : — 

" For as my arms I lifted to the skies, 

I saw black feathers from my fingers rise ; 

I strove to fling my garment on the ground ; 

My garment turned to plumes, and girt me round ; 

My hands to beat my naked bosom try ; 

Nor naked bosom now, nor hands had I; 

Lightly I tripp'd, nor weary as before 

Sunk in the sand, but skimm'd along the shore ; 

Till, rising on my wings, I was preferr'd 

To be the chaste Minerva's virgin bird " 

TELESCOPIC OBJECTS. 

1. /5 Corvi — A fine bright star nearly midway between two distant companions. A 2J$, 
ruddy yellow ; B 7, greenish yellow ; C 8, dull grey. (3 is actually the lucida, or brightest 
star of the constellation. 

2. 6 Corvi— A double star in the right wing ; R. A. 12h. 21m. 35s. ; Dec. S. 15° 37' 04'. 
A 3, pale yellow ; B 8%, purple. 



VIRGO (the virgin).— MAP IV. 

160. This is the sixth sign, and seventh constellation in the 
ecliptic. It is situated next east of Leo, and about midway 
between Coma Berenices on the N. and Corvus on the S. It 
occupies a considerable space in the heavens, and contains, 
according to Flamsted, one hundred and ten stars, including one 
of the 1st, six of the 3d, and ten of the 4th magnitudes. Its 
mean declination is 5° N., and its mean right ascension is 195°. 
Its center is therefore on the meridian about the 23d of May. 

The sun enters the sign Virgo, on the 23d of August, but does not enter the constella- 
tion before the 15th of September. When the sun is in this sign, the earth is in Pisces ; 
and vice versa. 

161. Alpha, or Spica Virginis, in the ear of corn which the 
virgin holds in her left hand, is the most brilliant star in this 
constellation, and situated nearly 15° E. N. E. of Algorab in 
the Crow, about 35° S. E. of Denebola, and nearly as far S. S. 

Telescopic Objects.— Beta ? Delta? «„„„ 

160. Order and position of Virgo ? Extent? Number of stars ? Magnitudes? Mean 

declination of Virgo ? Remark in fine print ? 161. What said of Alpha, or Spica Vir- 



VIRGO. 81 

W. of Arcturus — three very brilliant stars of similar magnitude 
that form a large equilateral triangle, pointing to the S. Arc- 
turus and Denebola are also the base of a similar triangle on 
the north, terminating in Cor Caroli, which, joined to the former, 
constitutes the Diamond of Virgo. 

162. The length of this figure, from Cor Caroli, on the north, 
to Spica Yirginis on the south, is 50°. Its breadth, or shorter 
diameter, extending from Arcturus on the east to Denebola on 
the west, is 35^-°. Spica may otherwise be known by its soli- 
tary splendor, there being no visible star near it except one of 
the 4th magnitude, situated about 1° below it, on the left. 

The position of this star in the heavens, has been determined with great exactness for 
the benefit of navigators. It is one of the staakfrom which the moon's distance is taken 
for determining the longitude at sea. Its situation is highly favorable for this purpose, 
as it lies within the moon's path, and little more than 2° below the earth's orbit. 

Its right ascension being 199", it will come to our meridian at 9 o'clock about the 28th 
of May, in that point of the heavens where the sun is at noon about the 20th of October. 

163. Beta, called also Zavijava, is a star of the 3d magni- 
tude, in the shoulder of the wing, 1-J- W. of Eta, with which 
and G-amma it forms a line near the Earth's orbit, and parallel 
to it. Beta, Eta, Gamma and Spica, form the lower and longer 
side of a large spherical triangle whose vertex is in Beta. 

164. Vindemiatrix, is a star of the 3d magnitude, in the right 
arm, or northern wing of Virgo, and is situated nearly in a 
straight line with, and midway between Coma Berenices and 
Spica Yirginis. It is 19^-° S. W. of Arcturus, and about 
the same distance S. E. of Coma Berenices, and forms with these 
two a large triangle, pointing to the south. It bears also 18° 
S. S, E. of Denebola, and comes to the meridian about 23 
minutes before Spica Virginis. 

165. Zeta, is a star of the 3d magnitude, 11^-° N. of Spica, 
and very near the equinoctial. Gamma, situated near the left 
side, is also a star of the 3d magnitude, and very near the equi- 
noctial. It is 13° due west of Zeta, with which and Spica it 
forms a handsome triangle. Eta, is a star of the 3d magnitude 
in the southern wing, 5° W. of Gamma, and but 2-J-° E. of the 
autumnal equinox. 

The other stars in this figure may be easily traced by means of the map. About 13° E. 
of Spica, there are two stars of the 4th magnitude, 3° apart, which mark the foot of Virgo. 
These two stars are on nearly the same meridian with Arcturus, and culminate nearly 
at the same time. The lower one, marked Lambda, is on the south, and but 8° W. of 
the principal star in Libra. Several other stars of the 3d magnitude lie scattered about 
in this constellation, and may be traced out by the map. 

ginis? Diamond? 162. Length of Virgo? Breadth? How may Spica be known? 
Note in fane print? 163. Describe Beta? What triangle? 164. Vindematrix? 

165. Zeta, Gamma and Eta ? What other stars and how found? 



82 ASTRONOMY. 

" Her lovely tresses glow with starry light ; 
Stars ornament the bracelet on her hand; 
Her vest in ample fold, glitters with stars : 
Beneath her snowy feet they shine ; her eyes 
Lighten, all glorious, with the heavenly rays, 
Butjirst the star which crowns the golden sheaf." 

HISTORY. 

According to the ancient poets, this constellation represents the Virgin Astrsea, the 
goddess of justice, who lived upon the earth during the golden age ; but being offended 
at the wickedness and impiety of mankind during the brazen and iron ages of the world, 
she returned to heaven, and was placed among the constellations of the zodiac, with a 
pair of scales (Libra) in one hand and a sword in the other. 

Hesiod, who flourished nearly a thousand years before the birth of our Saviour, and 
later writers, mention four ages of the world ; the golden, the silver, the brazen, and the 
iron age. In the beginning of things, say they, all men were happy, and all men were 
good ; the earth brought forth her fruits without the labor of man ; and cares, and 
wants, wars and diseases, were unknown. But this happy state of things did not last 
long. To the golden age, the silver age succeeded ; to the silver the brazen ; and to the 
brazen, the iron. Perpetual spring no l<^^er reigned; men continually quarreled with 
each other ; crime succeeded to crime ; and blasphemy and murder stained the history 
of every day. In the golden age, the gods did not disdain to mix familiarly with the 
sons of men. The innocence, the integrity and brotherly love which they found among 
us, were a pleasing spectacle even to superior natures; but as mankind degenerated, 
one god after another deserted their late beloved haunts; Astrsea lingered the last; but 
finding the earth steeped in human gore, she herself flew away to the celestial regions. 

" Victa jacet pietas ; et virgo csede madentes 

Ultima ccelestum terras Astrsea reliquit." 
Met. Lib. i. v. 149. 
" Faith flees, and piety in exile mourns ; 

And justice here oppress'd, to heaven returns." 

Some, however, maintain, that Erigone was changed into the constellation Virgo. The 
death of her father Icarus, an Athenian, who perished by the hands of some peasants, 
whom he had intoxicated with wine, caused a fit of despair, in which Erigone hung her- 
self; and she was afterward, as it is said, placed among the signs of the zodiac. She 
was directed by her faithful dog Msera to the place where her father was slain. The 
first bough on which she hung herself breaking, she sought a stronger, in order to effect 
her purpose. 

" Thus once in Marathon's impervious wood, 
Erigone beside her father stood, 
When hastening to discharge her pious vows, 
She loos'd the knot, and cull'd the strongest boughs." 
Lewis' Statius, B. xi. 

The famous zodiac of Dendera, as we have already noticed, commences with the sign 
Leo; but another zodiac, discovered among the ruins at Esne, in Egypt, commences with 
Virgo; and from this circumstance, some have argued, that the regular precession of 
the equinoxes established a date to this at least 2000 years older than that at Dendera. 
The discoveries of Champollion, however, render it probable that this ancient relic of 
astrology at Esne was erected during the reign of the Emperor Claudius, and conse- 
quently did not precede the one at Dendera more than fourteen years. 

Of this, however, we may be certain : the autumnal equinox now corresponds with 
the first degree of Virgo; and, consequently, if we find a zodiac in which the summer 
solstice was placed where the autumnal equinox now is, that zodiac carries us back 90° 
on the ecliptic; this divided by the annual precision 5054" must fix the date at about 
6450 years ago. This computation, according to the chronology of the Sacred writings, 
carries us back to the earliest ages of the human species on earth, and proves, at least, 
that astronomy was among the first studies of mankind. The most rational way of 
accounting for this zodiac, says Jamieson, is to ascribe it to the family of Noah ; or per- 
haps to the patriarch himself, who constructed it for the benefit of those who should live 
after the deluge, and who preserved it as a monument to perpetuate the actual state of 
the heavens immediately subsequent to the creation. 

History. — Account of the poets? Hesiod's account? What other supposition? What 
zodiacs mentioned, and what calculations, &c. ? 



CANES VENATICI. 83 



TELESCOPIC OBJECTS. 



1. a Virginis {Spica) — A splendid star with a minute companion ; R. A. 13h. 16m. 47s. ; 
Dec. S. JO" 19' 5". A 1, brilliant flushed white; B 10, bluish tinge. 

2. /3 Virginis (Zarijan) — A bright star with a small companion; R. A. llh. 42m. 22s. ; 
Dec. N. 2° 40' 0". A 3%, pale yellow ; B 11, light blue. 

3. y Virginis— A fine binary star in the Virgin's right side ; R. A. 12h. 33m. 33s. ; Dec. 
S. 0° 34' 3". A 4, silvery white ; B 4, pale yellow. A Binary System with a period of 
about 157 years. Map. VIII. Fig. 8. 

4. 6 Virginis — A star with a distant companion, on the left side, about 17° north-north- 
west of Spica, and nearly midway between y and e Virginis ; R. A. 12h. 47m. 33s. ; Dec. 
N. 4° 16' 1°. A 3%, golden yellow ; B 10%, reddish; several small stars in the field. 

5. e Virginis {Vendemiatrix) — A star with a minute distant companion, on the upper 
extremity of the Virgin's left wing ; R. A. 12h. 54m. 13s. ; Dec. 11° 49' 03". A 3%, bright 
yellow; B 15, intense blue. This last color on so small an object is very striking. 

6. A triple star in the lower part of the southern wing, 7° northwest of Spica ; R. A. 
I3h. 01m. 40s. ; Dec. S. 4° 41' 0". A 4%, pale white ; B 9, violet ; C 10, dusky. 

7. A large, but rather pale nebula, between Virgo's left wing and Leo's tail ; R. A. 
12h. 06m. 01s. ; Dec. N. 15° 47' 02". About 6%° from /? Leonis, towards Arcturus, on the 
outskirts of a vast region of Nebula in the Virgin's wing. It is elongated in the direction 
of two telescopic stars. 

8. A long pale-white nebula, among telescopic stars, on the upper part of the Vir- 
gin's left wing ; R. A. 12h. 07m. 37s. ; Dec. N. 14° 02' 08". Situated one-third of the way 
from j3 Leonis to e Virginis, on the border of the vast nebulous region in Virgo. A 
curious object in the shape of a weaver's shuttle. 

9. A lucid white elliptical nebula, between the Virgin's right elbow and the Crow ; 
R. A. 12h. 31m. 40s. ; Dec. S. 10° 43' 07". Map VILL, Fig. 45. 

10. A double nebula in the center of Virgo's left wing ; R. A. 12h. 35m. 33s. ; Dec. N. 
12° 26' 01". It is 5° west of Vendemiatrix, toward Regulus, in a wonderful nebulous 
region. Map VHT., Fig. 46, shows it on the right, with two other nebulae, and several 
stars in the figure. 

11. A pale elliptical nebula, in the middle of the left wing; R. A. 12h. 44m. 50s. , 
Dec. N. 12° 05' 09". It looks like a paper kite, under an arch formed by three telescopic 
stars. Map. VIII., Fig. 47. 

12. A wonderful nebulous region, about 2Jg° from north to south, and 3° from east to 
west, is found on the left wing. It includes several of the objects described. For a 
drawing of this remarkable field, see Map VIII., Fig. 48. 



CAKES VENATICI (the greyhounds).— MAP IY. 

166. This modern constellation, embracing two in one, was 
made by Hevelius out of the unformed stars of the ancients 
which were scattered between Bootes on the east, and Ursa 
Major on the west, and between the handle of the Dipper on the 
north, and Coma Berenices on the south. 

These Hounds are represented on the celestial sphere as being in pursuit of the Great 
Bear, which Bootes is hunting round the pole of heaven, while he holds in his hand the 
leash by which they are fastened together. The northern one is called Asterion, and 
the southern one, Chara. 

Telescopic Objects. — Alpha? Beta? Gamma? Delta? Epsilon? What triple star ? 
Nebula ? Point out on the map. 

166. Situation of Canes Venatici ? By whom formed ? How represented ? Names of 
the hounds ? 



4* 



84 ASTRONOMY. 

161. The stars in this gronp are considerably scattered, and 
are principally of the 5th and 6th magnitudes ; of the twenty- 
five stars which it contains, there is but one sufficiently large to 
engage our attention. Cor Caroli or Charles' Heart, so named 
by Sir Charles Scarborough, in memory of King Charles the 
First, is a star of the 3d magnitude, in the neck of Chara, the 
southern Hound. 

When on the meridian, Cor Caroli is 17%° directly S. of Alioth, the third star in the 
handle of the Dipper, and is so nearly on the same meridian that it culminates only one 
minute and a half after it. This occurs on the 20th of May. 

A line drawn from Cor Caroli through Alioth will lead to the N. polar star. This star 
may also be readily distinguished by its being in a straight line with, and midway between 
Benetnasch, the first star in the handle of the Dipper, and Coma Berenices ; and also by 
the fact that when Cor Caroli is on the meridian, Denebola bears 28" S. W. and Arcturus 
26° S. E. of it, forming with these two stars a very large triangle, whose vertex is at the 
north ; it is also at the northern extremity of the large Diamond already described. 

The remaining stars in this constellation are too small and too much scattered to excite 
our interest. 

TELESCOPIC OBJECTS. 

1 A double star near Chara's mouth ; R. A. 12h. 08m. 06s. ; Dec. N. 41° 33' 01'. A 6, 
yellow ; B 9, blue. It is about 9° south of Cor Caroli, and one-third of the distance 
between that star and J Leonis. Map VIII., Fig. 10. 

2. A magnificent cluster, between the southern Hound and the knee of Bootes ; R. A. 
13h. 34m. 45s. A splendid group, supposed to contain not less than 1,000 stars. Map 
VIII., Fig. 49. 

8. A pair of lucid white nebui^e, near the ear of the northern Hound ; R. A. 13h. 23m. 
06s. ; Dec. N. 48' 01' 07'. 

4. A large bright nebula, 2^° north by west of Cor Caroli; R. A. 12h. 43m. 22s. ; Dec. 
N. 41° 59' 07". A fine pale-white object, compressed toward the center, and with several 
small stars in the field. 



CHAPTER VIII. 

CONSTELLATIONS ON THE MERIDIAN IN JUNE. 
BOOTES (THE BEAR DRIVER).— MAP IV. 

168. The B ear-Driver is represented by the figure of a hunts- 
man in a running posture, grasping a club in his right hand, and 
holding up in his left the leash of his two greyhounds, Asterion 
and Chara, with which he seems to be pursuing the Great Bear 
round the pole of the heavens. He is thence called Arcto- 
phylax, or the " Bear-Driver." 

167. Describe the stars in this group? Cor Caroli? 

Telescopic Objects. — What double star ? Show on the map ? Clusters? Point out on 
the map ? Nebulae ? 
1 68 Describe Bootes ? Why called the Bear-Driver ? 



BOOTES. &5 

169. This constellation is situated between Corona Borealis 
on the east, and Cor Caroli, or the Greyhounds, on the west. 
It contains fifty-four stars, including one of the 1st magnitude, 
seven of the 3d, and ten of the 4th. Its mean declination is 20° 
N., and its mean right ascension is 212° ; its center is there- 
fore on the meridian the 9th of June. It may be easily distin- 
guished by the position and splendor of its principle star, Arc- 
turns, which shines with a reddish luster, very much resembling 
that of the planet Mars. 

170. Arcturus is a star of the 1st magnitude, situated near 
the left knee, 26° S. E. of Cor Caroli and Coma Berenices, with 
which it forms an elongated triangle, whose vertex is at Arc- 
turus. It is 35^-° E. of Denebola, and nearly as far N. of Spica 
Yirginis, and forms with these two, as has already been observed, 
a large equilateral triangle. It also makes, with Cor Caroli and 
Denebola, a large triangle whose vertex is in Cor Caroli. 

A great variety of geometrical figures may be formed of the stars in this bright region 
of the skies. For example : Cor Caroli on the N., and Spica Virginis on the S., constitute 
the extreme points of a very large figure in the shape of a diamond ; while Denebola on 
the W. and Arcturus on the E., limit the mean diameter at the other points. 

1*11. Arcturus is supposed by some to be nearer the Earth 
than any other star in the northern hemisphere. 

Five or six degrees S. W. of Arcturus are three stars of the 8d and 4th magnitudes, 
lying in a curved line, about 2° apart, and a little below the left knee of Bootes ; and 
about 7° E. of Arcturus are three or four other stars of similar magnitude, situated in 
the other leg, making a larger curve N. and S. 

112. Mirac, in the girdle, is a star of the 3d magnitude, 10° 
K K E. of Arcturus, and about 11^-° W. of Alphacca, a star in 
the jNorthern Crown. Seginus, in the west shoulder, is a star 
of the 3d magnitude, nearly 20° E. of Cor Caroli, and about the 
same distance N. of Arcturus, and forms with these two, a right- 
angled triangle, the right angle being at Seginus. The same 
star forms a right-angled triangle with Cor Caroli and Alioth, 
in Ursa Major, the right angle being at Cor Caroli. 

173. Alkaturops, situated in the top of the club, is a star of 
the 4th magnitude, about 10-J- in an easterly direction from 
Seginus, which lies in the left shoulder ; and about 4-| S. of 
Alkaturops is another star of the 4th magnitude, in the club, 
near the east shoulder, marked Delta. Delta is about 9^ dis- 
tant from Mirac, and 7^-° from Alphacca, and forms, with these 
two, a regular triangle. 

169. How situated? How many stars, and their magnitude ? Declination? How dis- 
tinguished ? 170. Describe Arcturus, and its position ? What triangles ? What dia- 
mond? 171. Supposed nearness of Arcturus? 172. Describe Mirac and Seginus? 
What triangles ? 178. Situation and magnitude of Alkaturops ? Of Delta ? 



86 ASTRONOMY. 

114. Nekkar is a star of the 3d magnitude, situated in the 
head, and is about 6° JS T . E. of Seginus, and 5° W. of Alkatu- 
rops ; it forms, with Delta and Seginus, nearly a right angled 
triangle, the right angle being at Nekar. 

These are the principal stars in this constellation, except the three stars of the 4th 
magnitude situated in the right hand. These stars may be known by two of them being 
close together, and about 5° beyond Benetnasch, the first star in the handle of the Dip- 
per. About 6° E. of Benetnasch is another star of the 4th magnitude, situated in the 
arm which forms, with Benetnasch and the three in the hand, an equilateral triangle. 

175. The three stars in the left hand of Bootes, the first in 
the handle of the Dipper, Cor Caroli, Coma Berenices, and 
Denebola, are all situated nearly in the same right line, running 
from northeast to southwest. 

"Bootes follows with redundant light; 
Fifty-four stars he boasts ; one guards the Bear, 
Thence call'd Arcturus, of resplendent front, 
The pride of ike first order: eight are veil'd, 
Invisible to the unaided eye." 

Manilius thus speaks of this constellation : — 

" And next Bootes comes, whose order'd beams 
Present a figure driving of his teams. 
Below his girdle, near his knees, he bears 
The bright Arcturus, fairest of the stars." 

176. Arcturus is mentioned by name in that beautiful passage 
in Job, already referred to, where the Almighty answers "out 
of the Whirlwind," and says : — 

" Canst thou the sky's benevolence restrain, 
And cause the Pleiades to shine in vain? 
Or, when Orion sparkles from his sphere, 
Thaw the cold seasons and unbind the year? 
Bid Mazzaroth his wonted station know, 
And teach the bright Arcturus where to glow?" 

Young's Paraphrase. 

HISTORY. 

The ancient Greeks called this constellation Lycaon — a name derived from TiVKOS, 
which signifies a wolf. The Hebrews called it Caleb Anubae7b, the " Barking Dog;" 
while the Latins, among other names, called it Canis. If we go back to the time when 
Taurus opened the year, and when Virgo was the fifth of the zodiacal signs, we shall 
find that brilliant star Arcturus, so remarkable for its red and fiery appearance, corres- 
ponding with a period of the year as remarkable for its heat. Pythagoras, who intro- 
duced the true system of the universe into Greece, received it from (Enuphis, a priest of 
On, in Egypt. And this college of the priesthood was the noblest of the east, in cultivat- 
ing the studies of philosophy and astronomy. Among the high honors which Pharaoh 
conferred on Joseph, he very wisely gave him in marriage " a daughter of the priest of 
On." The supposed era of the book of Job, in which Arcturus is repeatedly mentioned, 
is 1513 B. C. 

Bootes is supposed by some to be Icarus, the father of Erigone, who was killed by 
shepherds for intoxicating them. Others maintain that it is Erichthonius, the inventor 
of chariots. According to Grecian fable, as well as later authorities, Bootes was the son 
of Jupiter and Calisto, and named Areas. Ovid relates, that Juno, being incensed at 
Jupiter for his partiality to Calisto, changed her into a bear, and that her son Areas, who 
became a famous hunter, one day roused a bear in the chase, and not knowing that it 

174. Of Nekkar ? Any other stars t lib. What said of three stars in the hand of 
Bootes ? 176. What star in Bootes mentioned in the Scriptures ? Poetic quotation ? 
History. — Greek name of this constellation ? Hebrew ? Grecian fable ? Ovid's 



BOOTES. 87 



was his mother, was about to kill her, when Jupiter snatched them both up to heaven 
and placed then among the constellations. Met. b. ii. v. 496-508. 

"But now her son had fifteen summers told, 
Pierce at the chase, and in the forest bold ; 
When as he beat the woods in quest of prey, 
He chanced to rouse his mother where she lay. 
She knew her son, and kept him in her sight, 
And fondly gazed : the boy was in a fright, 
And aim'd a pointed arrow at her breast ; 
And would have slain his mother in the beast: 
But Jove forbade, and snatch'd them through the air 
In whirlwinds up to heaven, and fix'd 'em there ; 
Where the new constellations nightly rise, 
And add a luster to the northern skies." 

GartWs Translation. 
Lucan, in his Pharsalia, says — 

u That Brutus, on the busy times intent, 
To virtuous Cato's humble dwelling went, 
'Twas when the solemn dead of night came on, 
When bright Calisto, tcithher shining son, 
Now half that circle round the pole had run." 

This constellation is called Bootes, says Cicero {Nat. Deo. Lib. ii. 42), from a Greek 
word signifying a wagoner, or ploughman ; and sometimes Arctophylax from two Greek 
words signifying bear-keeper or bear-driver. 

"Arctophylax, vulgo qui dicitur esse Bootes, 
Quod quasi temone adjunctum prse se quatit Arctum." 

The stars in this region of the skies seem to have attracted the admiration of almost 
all the eminent writers of antiquity. Claudian observes, that 
" Bootes with his wain the north unfolds ; 
The southern gate Orion holds." 

And Aratus, who flourished nearly 800 years before Claudian, says, 
"Behind, and seeming to urge on the Bear, 
Arctophylax, on earth Bootes named, 
Sheds o'er the Arctic car his silver light." 

This is the poet whom St. Paul refers to when he tells the Athenians, Acts xvii. 28, that 
" some of their own poets have said, ' Tov yap /cat yevos eafiev :' For we are also 
his offspring." These words are the beginning of the 5th line of the "Phenomena" of 
Aratus, a celebrated Greek poem written in the reign of Ptolemy Philadelphus, two 
thousand one hundred years ago, and afterward translated into Latin verse by Cicero. 
Aratus was a poet of St. Paul's own country. The apostle borrows again from the same 
poet, both in his Epistle to the Galatians, and to Titus. The subject of the poem was 
grand and interesting: hence we find it referred to in the writings of St. Clement, St. 
Jerome, St. Chrysostom, CEcumenius, and others. As this poem describes the nature and 
motions of the stars, and the origin of the constellations, and is, moreover, one of the 
oldest compositions extant upon this interesting subject, the author has taken some 
pains to procure a Polyglot copy from Germ any, together with the Astronomicon of 
Manilius, and some other works of similar antiquity, that nothing should be wanting on 
his part which could impart an interest to the study of the constellations, or illustrate 
the frequent allusions to them which we meet with in the Scriptures. 

Dr. Doddridge says of the above quotation, that " these words are well known to be 
found in Aratus, a poet of Paul's own country, who lived almost 300 years before the 
apostle's time; and that the same words, with the alteration of only one letter, are to 
be found in the Hymn of Cleanthes, to Jupiter, the Supreme God; which is, beyond 
comparison, the purest and finest piece of natural religion, of its length, which I know 
in the whole world of Pagan antiquity ; and which, so far as I can recollect, contains 
nothing unworthy of a Christian, or, I had almost said, of an inspired pen. The apostle 
might perhaps refer to Cleanthes, as well as to his countryman Aratus." 

Many of the elements and fables of heathen mythology are so blended with the 

account? Lucan and Cicero? Claudian? Aratus? Who was Aratus ? What remark, 
able quotation ? Remark of Doddridge ? What other passage cited by St. Paul ? From 
whom? 



88 ASTRONOMY. 

inspired writings, that they must needs be studied, more or less, in order to have a more 
proper understanding of numerous passages both in the Old and New Testament. 

The great apostle of the Gentiles, in uttering his inspired sentiments, and in penning 
his epistles, often refers to and sometimes quotes verbatim from the distinguished writers 
who preceded him. 

Thus, in 1 Cor. xv. 33, we have " M77 Trlavasde ' ' Qdetpovcuv rjdrj XPV^' Ofiiktai 
tca/cai.' Be not deceived; evil communications corrupt good manners;" which is a 
literal quotation by the apostle from the Thais of Menander, an inventor of Greek 
comedy, and a celebrated Athenian poet, who flourished nearly 400 years before the 
apostle wrote his epistle to the Corinthians. Thus Paul adopts the sentiment of the 
comedian, and it becomes hallowed by " the divinity that stirred within him." Tertul- 
lian remarks, that " in quoting this, the apostle hath sanctified the poet's sentiment." 

TELESCOPIC OBJECTS. 

1. a Bootis (Arcturus) — A double star ; R. A. 14h. 08m. 22s. ; Dec. N. 20° 00' 9". A 1, 
reddish yellow ; B 11, lilac. 

2. /? Bootis (Nekkar) — A star with a distant companion in the head of the figure ; R. A. 
14h. 55m. 55s. ; Dec. N. 41° 01' 5". A 3, golden yellow : B 11, pale grey. 

3. 6 Bootis — A star with a distant companion in the left shoulder ; R. A . 15h. 09m. 03s.; 
Dec. N. 33° 54' 9". A 3%, pale yellow; B 8 %, light blue. 

4. e Bootis (Mirac) — A double star in the left hip ; R. A. 14h. 38m. 00s. ; Dec. N. 27° 
45' 1". A 3, pale orange ; B 7, sea green. A lovely object — colors distinct, and strongly 
contrasted. 

5. £" Bootis— A close double star on the left leg ; R. A. 14h. 33m. 31s. ; Dec. N. 14° 25' 
1*. A 3%, bright white ; B 4%, bluish white. 

6. 77 Bootis (Mufride) — A star with a distant companion on the right leg ; R. A. 13h. 
47m. 04s. ; Dec. N. 19° 12' 0". About 5j£° west by south of Arcturus. A 3, pale yellow ; 
B 10 %, lilac. 

7. 1 Bootis — A delicate triple star in the right hand (Map VI.) ; R. A. 14h. 10m. 30s.; 
Dec. N. 52° 06' 4". A and B 4%, pale yellow ; C 8, creamy white. 

8. £ Bootis — A binary star on the left knee ; R. A. 14h. 44m. 00s. ; Dec. N. 19° 46' 1*. 
A 3%, orange ; B6J^, purple. Supposed period 400 years. 

9. A rich group of stars in the vicinity of Arcturus, and surrounding that star. May 
be seen with small telescopes. Map VIIL, Fig. 50. 

10. A pale white nebula in a nebulous field, 5° north northeast of Alkaid ; R. A. 
13h. 57m. 31s. ; Dec. N. 55° 08' 3°. About 5° southeast of Mizwr. A difficult object 
except with a good instrument. 

11. A white round nebula near the right shoulder ; R. A. 14h. 11m. 44s. ; Dec. N. 37* 
14' 4". Pale, except at the center — telescopic stars in the field. 



NOCTA (the owl).— MAP IV. 

I'll. This small asterismis situated between the feet of Virgo, 
on the north, and the tail of Hydra, on the south. It has but few 
stars, and those only of the 5th and 6th magnitudes. It is often 
omitted altogether from the constellations. 



CEOTAUKUS (the oentatje).— MAP IV. AND VII. 

178. This fabulous monster is represented by the figure of a 
man, terminating in the body of a horse, holding a wolf at arm's 

Telescopic Objects.— Alpha ? Beta? Delta? Epsilon? Zeta? Eta? Iota? Xi? 
What rich group ? Point out on the map. What nebulae ? 
177. Describe Nocta, its situation, stars, &c. 



CENTAURUS. 89 

length in one hand, while he transfixes its body with a spear in 
the other. 

Although this constellation occupies a large space in the 
southern hemisphere, yet it is so low down that the main part 
of it cannot be seen in our latitude. It is situated south of 
Spica Yirginis, with a mean declination of 50°. It contains 
thirty-five stars, including two of the 1st magnitude, one of the 
2d, and six of the 3d ; the brightest of which are not visible in 
the United States. 

179. Theta is a star of between the 2d and 3d magnitude, in 
the east shoulder, and may be seen from this latitude, during the 
month of June, being about 21° S. by E. from Spica Yirginis, 
and 12° or 13° above the southern horizon. It is easily recog- 
nized in a clear evening, from the circumstance that there is no 
other star of similar brightness in the same region, for which it 
can be mistaken. It is so nearly on the same meridian with 
Arcturus that it culminates but ten minutes before it. 

Iota is a star of between the 4th and 5th magnitude, in the west shoulder, 9H° W. of 
Theta. It is about 26° almost directly south of Spica Virginis, and is on the meridian 
nearly at the same time. 

Mu and IPic are stars of the 4th magnitude, in the breast, very near together, and form 
a regular triangle with the two stars in the shoulders. 

A few degrees north of the two stars in the shoulders, are four small stars in the head. 
The relative position of the stars in the head and shoulders is very similar to that of the 
stars in the head and shoulders of Orion. 

HISTORY. 

Centaurs, in mythology, were a kind of fabulous monsters, half men and half horses. 
This fable is, however, differently interpreted; some suppose the Centaurs to have been 
a body of shepherds and herdsmen, rich in cattle, who inhabited the mountains of Arca- 
dia, and to whom is attributed the invention of pastoral poetry. But Plutarch and Pliny 
are of opinion that such monsters have really existed. Others say, that under the reign 
of Ixion, king of Thessaly, a herd of bulls ran mad, and ravaged the whole country, 
rendering the mountains inaccessible ; and that some young men, who had found the art 
of taming and mounting horses, undertook to expel these noxious animals, which they 
pursued on horseback, and thence obtained the appellation of Centaurs. 

This success rendering them insolent, they insulted the Lapithae, a people of Thessaly ; 
and because, when attacked, they fled with great rapidity, it was supposed that they 
were half horses and half men ; men on horses being at that period a very uncommon 
sight, and the two appearing, especially at a distance, to constitute but one animal. So 
the Spanish cavalry at first seemed to the astonished Mexicans, who imagined the horse 
and his rider, like the Centaurs of the ancients, to be some monstrous animal of a ter- 
rible form. 

The Centaurs, in reality, were a tribe of Lapithae, who resided near Mount Pelion, and 
first invented the art of breaking horses, as intimated by Virgil. 

"The Lapithae to chariots add the state 
Of bits and bridles ; taught the steed to bound 
To turn the ring, and trace the mazy ground ; 
To stop, to fly, the rules of war to know; 
To obey the rider, and to dare the foe." 
Centaurus is so low down in the south that it would be of no service to describe its tele 
6copic objects. 

178. How is Centaurus represented ? Its situation ? Number of stars, &c? 179. Theta 
lot a, Mu, Nu, Ac? 

History. — What was Centaurus ? Different opinions ? 



90 ASTRONOMY. 



LUPUS (the wolf).— MAPS Y. AND VII. 

180. This constellation is situated next east of the Centaur, 
and south of Libra ; and is so low down in the southern hemi- 
sphere, that only a few stars in the group are visible to us. It 
contains twenty-four stars, including three of the 3d magnitude, 
and as many of the 4th ; the brightest of which, when on the 
meridian, may be seen in a clear evening, just above the southern 
horizon. Their particular situation, however, will be better 
traced out by reference to the map than by written directions. 

The most favorable time for observing this constellation is 
toward the latter end of June. 

HISTORY. 

This constellation, according to fable, is Lycaon, king of Arcadia, who lived about 3600 
years ago, and was changed into a wolf by Jupiter, because he offered human victims on 
the altars of the god Pan. Some attribute this metamorphosis to another cause. The 
sins of mankind, as they relate, had become so enormous, that Jupiter visited the earth 
to punish its wickedness and impiety. He came to Arcadia, where he was announced as 
a god, and the people began to pay proper adoration to his divinity. Lycaon, however, 
who used to sacrifice all strangers to his wanton cruelty, laughed at the pious prayera 
of his subjects, and to try the divinity of the god, served up human flesh on his table. 
This impiety so offended Jupiter, that he immediately destroyed the house of Lycaon, 
and changed him into a wolf. 

" Of these he murders one ; he boils the flesh, 
And lays the mangled morsels in a dish ; 
Some part he roasts ; then serves it up so dress'd, 
And bids me welcome to his human feast. 
Moved with disdain, the table I o'erturned, 
And with avenging flames the palace burn'd. 
The tyrant in a fright for shelter gains 
The neighboring fields, and scours along the plains: 
Howling he fled, and fain he would have spoke, 
But human voice his brutal tongue forsook. 
His mantle, now his hide, with rugged hairs, 
Cleaves to his back : a famish'd face he bears ; 
His arms descend, his shoulders sink away 
To multiply his legs for chase of prey ; 
He grows a wolf." — Ovid. Met. B. i. 

TELESCOPIC OBJECTS. 

1. a Lupi— -A star with a distant companion, in the tail of Lupus ; R. A. 5h. 25m. 
40s. ; Dec. S. 17° 56' 5". A 3%, pale yellow ; B 9%, grey. To find, draw a line from e 
the central star of Orion's belt, through 6 and its nebulous patch on the sword, as low 
down, and Sinus, and you meet a Lupi. 

2. Lupi— A double star ; R. A. 5h. 21m. 23s. ; Dec. S. 20° 53' 5". A '4, deep yel- 
low ; B 11, blue. 

3. y Lupi — A wide triple star in a barren field ; R. A. 5h. 37m. 48s. ; Dec. 22° 
30' 2". A 4, light yellow ; B 6%, pale green ; C 13, dusky. A line from 6 Orionis through 
the second cluster, and carried 16° beyond, falls upon it. 

4. A bright stellar nebula, of a milky white tinge ; R. A. 5h. 17m. 50s. Dec. S. 24° 
39' 9". A fine object blazing towards the centre. 



ISO. Situation of Lupus ? Number and magnitude of its stars ? Best time to observe ? 
History. — What was Lupus originally? Why changed and by whom? Described by 
what poet? 
Telescopic Objects. — Alpha? Beta? Gamma? What Nebula? 



JBRA. 91 



LIBEA (the scales).— MAP IV. A^ T D V. 

181. This is the seventh sign, and eighth constellation, from 
the vernal eqninox, and is situated in the Zodiac, next east of 
Yirgo. 

The snn enters this sign, at the autumnal equinox, on the 23d 
of September ; but does not reach the constellation before the 
2Tth of October. When the sun enters the sign Libra, the 
days and nights are equal all over the world, and seem to 
observe a kind of equilibrium, like a balance. 

When, however, it is said that the vernal and autumnal equinoxes are in Aries and 
Libra, and the tropics in Cancer and Capricorn, it must be remembered that the signs 
Aries and Libra, Cancer and Capricorn, and not the constellations of these names, are 
meant: for the equinoxes are now in the constellations Pisces and Virgo, and the tropics 
in Gemini and Sagittarius ; each constellation having gone forward one sign in the 
ecliptic. 

About 22 centuries ago, the constellation Libra coincided with the sign Libra ; but 
having advanced 30° or more in the ecliptic, it is now in the sign Scorpio, and the con- 
stellation Scorpio is in the sign Sagittarius, and so on. 

While Aries is now advanced a whole sign above the equinoctial point into north decli- 
nation, Libra has descended as far below it into south declination. 

182. Libra contains fifty-one stars, including two of the 2d 
magnitude, two of the 3d, and twelve of the 4th. Its mean 
declination is 8° south, and its mean right ascension 226°. Its 
center is therefore on the meridian about the 22d of June. 

It may be known by means of its four principal stars, forming 
a quadrilateral figure, lying northeast and southwest, and 
having its upper and lower corners nearly in a line running north 
and south. The two stars which form the N..E. side of the 
square, are situated about 7° apart, and distinguish the Northern 
Scale. The two stars which form the S. W. side of the square 
are situated about 6° apart, and distinguish the Southern Scale. 

Zubenescharnali, in the Southern Scale, about 21° E. of Spica, and 8° E. of Lambda 
Virginis, is a star of the 2d magnitude, and is situated very near the ecliptic, about 42 3^° 
E. of the autumnal equinox. The distance from this star down to Theta Centauri is 
about 23°, with which, and Spica Virginis, it forms a large triangle, on the right. 

Zubenelgemabi, the uppermost star in the Northern Scale, is also of the 2d magnitude, 
9%° above Zubenescharnali, toward the northeast, and it comes to the meridian about 
twenty-six minutes after it, on the 23d of June. Zubenelgemabi is the northernmost of 
the four bright stars in this figure, and is exactly opposite the lower one, which is 11° 
south of it. 

Zatbenhakrabi is a star of the 3d magnitude in the Northern Scale, 7° S. E. of Zubenel- 
gemabi, and nearly opposite to Zubenescharnali, at the distance of 11° on the east. 
These two make the diagonal of the square east and west. 

Iota is a star of the 4th magnitude, and constitutes the southernmost corner of the 
square. It is about 6° S. E. of Zubenescharnali, and 11° S. of Zubenelgemabi, with which 
it forms the other diagonal north and south. 

Zebenelgubi is a star of the 3d magnitude, situated below the Southern Scale, at the 

181. Order and situation of Libra? What circumstance suggesting a balance? What 
remarks respecting the distinction between the signs and the constellations ? 1S2. Num- 
ber of stars in Libra ? Its mean decimation ? Eight ascension ? When on the meri- 
dian? How may it be known? Describe the four stars. Closing remarks ? 



92 ASTRONOMY. 

distance of 6° from Iota, and marks the southern limit of the Zodiac. It is situated In a 
right line with, and nearly midway between Spica Virginia and Beta Scorpionis : and 
comes to the meridian nearly at the same moment with Nekkar, in the head of Bootes. 

The remaining stars in this constellation are too small to engage attention. 

The scholar, in tracing out this constellation in the heavens, will perceive that Lambda 
and Mu, which lie in the feet of Virgo on the west, form, with Zubeneschamali and 
Zubenelgemabi, almost as handsome and perfect a figure, as the other two stars in the 
Balance do on the east. 

HISTORY. 

Virgo was the goddess of justice, and Libra, the scales, which she is usually repre- 
sented as holding in her left hand, are the appropriate emblem of her office. 

The Libra of the Zodiac, says Maurice, in his Indian Antiquities, is perpetually seen 
upon all the hieroglyphics of Egypt ; which is at once an argument of the great antiquity 
of this asterism, and of the probability of its having been originally fabricated by the 
astronomical sons of Misraim. In some few zodiacs, Astrsca, or the virgin who holds the 
balance in her hand as an emblem of equal justice, is not drawn. Such are the zodiacs 
of Esne and Dendera. Humboldt is of opinion, that although the Romans introduced 
this constellation into their zodiao in the reign of Julius Ca3sar, still it might have been 
used by the Egyptians and other nations of very remote antiquity. 

It is generally supposed that the figure of the balance has been used by all nations to 
denote the equality of the days and nights, at the period of the sun's arriving at this 
sign. It has also been observed, that at this season there is a greater uniformity in the 
temperature of the air all over the earth's surface. 

Others affirm, that the team only of the balance was at first placed among the stars, 
and that the Egyptians thus honored it as their Nilometer, or instrument by which they 
measured the inundations of the Nile. To this custom of measuring the waters of the 
Nile, it is thought the prophet alludes, when he describes the Almighty as measuring 
the waters in the hollow of his hand. — Isa. xl. 12. 

The ancient husbandmen, according to Virgil, were wont to regard this sign as indi 
eating the proper time for sowing their winter grain : — 

" But when Astrsea's balance, hung on high, 
Betwixt the nights and days divides the sky, 
Then yoke your oxen, sow your winter grain, 
Till cold December comes with driving rain." 

The Greeks declare that the balance was placed among the stars to perpetuate the 
memory of Mochus, the inventor of weights and measures. 

Those who refer the constellations of the Zodiac to the twelve tribes of Israel ascribe 
the Balance to Asher. 

TELESCOPIC OBJECTS. 

1. a Librae— A wide double stab ; R. A. 14h. 42m. 02s. ; Dec. S. 15° 22' 3\ A 3, pale 
yellow ; B 6, light grey. Carry a line from Arcturus to Spica ; and from thence a rect- 
angular one about 22° to the eastward. 

2. ft Librae— A loose double star ; R. A. 15h. 08m. 24s. ; Dec. S. 8° 47' 4". A 2%, pale 
emerald ; B 12, light blue. 

3. £ Librae — A fine triple star, between Libra and the right leg of Ophiuchus, 16° from 
Antares, towards Serpentis ; R. A. 15h. 55m. 35s.; Dec. S. 10° 55' 6". A 4%, bright 
white ; B 5, pale yellow; C 7%, grey. Map VIII., Fig. 11. 

4. A close cluster, over the beam of the Scales ; R. A. 15h. 10m. 26s. ; Dec. N. 2° 41' 3". 
A superb object, with a bright central blaze, and outlines in all directions. Map IX., 
Eig. 51. Appears nebulous through small instruments. 

5. A large compressed cluster of minute stars ; R. A. 15h. 08m. 06s. ; Dec. S. 20° 26' 7". 
Faint and pale. 

History. — Who was Virgo, &c. ? Remark of Maurice ? What general supposition? 
What other explanations ? 
Telescopic Objects. — Alpha? Beta? What triple star ? Map? Clusters and Map ? 



ERPENS. 93 



SERPENS (the serpent).— PLATE Y. 

183. There are- no less than four kinds of serpents placed 
among the constellations. The first is the Hydra, which is situ- 
ated south of the Zodiac, below Cancer, Leo and Virgo ; the 
second is Hydrus, which is situated near the south pole; the 
third is Draco, which is situated about the north pole ; and the 
fourth is the serpent called Serpens Ophiuchi, and is situated 
chiefly between Libra and Corona Borealis. A large part of 
this constellation, however, is so blended with Ophiuchus, the 
Serpent-Bearer, who grasps it in both hands, that the concluding 
description of it will be deferred until we come to that constel- 
lation. 

" The Serpens Ophiuchi -winds his spire 
Immense: fewer by ten his figure trace; 
One of the second rank ; ten shun the sight ; 
And seven, he who bears the monster hides." 

184. Those stars which lie scattered along for about 25°, in a 
serpentine direction between Libra and the Crown, mark the 
body and head of the Serpent. 

About 10° directly S. of the Crown there are three stars of 
the 3d magnitude, which, with several smaller ones, distinguish 
the head. 

185. Unuk, of the 2d magnitude, is the principal star in this 
constellation. It is situated in the heart, about 10° below those 
in the head, and may be known by its being in a line with, and 
between, two stars of the 3d magnitude — 'the lower one, marked 
Epsifon, being 2£°, and the upper one, marked Delta, about 5-J° 
from it. The direction of this line is N. M". W. and S. S. E. 
Unuk may otherwise be known by means of a small star, just 
above it, marked Lambda. 

In that part of the Serpent which lies between Corona Borealis and the Scales, about 
a dozen stars may be counted, of which fire or six are conspicuous. 
For the remainder of this constellation, the student is referred to Serpentarius. 

"Vast as the starry Serpent, that on high 
Tracks the clear ether, and divides the sky, 
And southward winding from the Northern Wain. 
Shoots to remoter spheres its glittering train." — Statins. 

HISTORY. 

The Hivites, of the Old Testament, were worshipers of the Serpent, and were called 
Ophites. The idolatry of these Ophites was extremely ancient, and was connected with 

183. How many serpents among the constellations? Describe each. Which here 
referred to? Is it fully described ? 184. What stars mark the body and head ? 185. 
Name the principal star. Where situated and how known T 

History. — What said of the Hivites? Tradition respecting Ophiuchus? Supposed 
Scripture reference ? 



94 ASTRONOMY. 

Scbbeism, or the worship of the host of heaven. The heresy of the Ophites, mentioned 
by Mosheim, in his Ecclesiastical History, originated, perhaps, in the admission into the 
Christian church of some remnant of the ancient and popular sect of Sabeists, who 
adored the celestial Serpent. 

According to ancient tradition, Ophiuchus is the celebrated physician JSsculapius, son 
of Apollo, who was instructed in the healing art by Chiron the Centaur; and the ser- 
pent, which is here placed in his hands, is understood by some to be an emblem of his 
sagacity and prudence ; while others suppose it was designed to denote his skill in heal- 
ing the bite of this reptile. Biblical critics imagine that this constellation is alluded to 
in the following passage of the book of Job : — 

" By his spirit He hath garnished the Heavens ; his hand hath formed the crooked ser- 
pent." Mr. Green supposes, however, that the inspired writer here refers to Draco, 
because it is a more obvious constellation, being nearer the pole where the constellations 
were more universally noticed ; and moreover, because it is a more ancient constellation 
than the Serpent, and the hieroglyphic by which the Egyptians usually represented the 
heavens. 

TELESCOPIC OBJECTS. 

1. a Serpentis (JJnuk) — A star with a minute companion on the heart of the Serpent; 
R. A. 15h. 36m. 23s. ; Dec. N. 6° 55' 9". A 2%, pale yellow ; B 15, fine blue. An extremely 
delicate object. 

2. j3 Serpentis — A delicate double star in the Serpent's under jaw ; R. A. 15h. 38m. 
48s. ; Dec. N. 15° 55' 7". A 3%, and B 10, both pale blue. 

3. 6 Serpentis — An elegant double star in the bend of the neck ; R. A. 15h. 27m. 10s. ; 
Dec. N. 11° 04' 7". A 3, bright white ; B 5, bluish white. A fine object, about 5° N. W. 
of Unak. 

4. 7] Serpentis — A star with a minute companion in the Serpent's body, nearly midway 
between 7] Ophiuchi and a Aquilse; R. A. 18h. 13m. 02s. ; Dec. S. 2° 56' 0°. A 4, golden 
yellow; B 13, pale lilac. A delicate and difficult object. 

5. v Serpentis — A wide double star in the middle of the Serpent, 4° northeast of 7] "> 
R. A. 17h. 11m. 49s. ; Dec. S. 12° 40' 7"- A 4%, pale sea-green ; B 9, lilac, with a third 
star in the field. 

6. A delicate double star ; R. A. 15h. 11m. 08s. ; Dec. N. 2° 22' 6". A 5%, pale yellow 
B 10%, light grey. Look 9° southwest of a Serpentis, 24° southeast of Arcturus. 



CORONA BOREALIS (the northern grown).— MAP V. 

186. This beautiful constellation may be easily known by 
means of its six principal stars, which are so placed as to form 
a circular figure, very much resembling a wreath or crown. It 
is situated directly north of the Serpent's head, between Bootes 
on the west, and Hercules on the east. 

This asterism was known to the Hebrews by the name of Ataroth, and by this name 
the stars in Corona Borealis are called, in the East, to this day. 

181. Alphacca, of the 2d magnitude, is the brightest and 
middle star in the diadem, and about 11° E. of Mirac, in Bootes. 
It is very readily distinguished from the others both on account 
of its position and superior brilliancy. Alphacca, Arcturus, and 
Seginus, form nearly an isosceles triangle, the vertex of which is 
at Arcturus. 



Telescopic Objects.— Alpha ? Beta? Delta? Eta? Nu? &c. 

186. How may Corona Borealis be known? Where situated? Its Hebrew name? 
187. Describe Alphacca? How distinguished? What triangle ? 



CORONA BOREALIS. 95 

188. This constellation contains twenty-one stars, of which 
only six or eight are conspicuous ; and most of these are not 
larger than the 3d magnitude. Its mean declination is 30° 
north, and its mean right ascension 235°; its center is therefore 
on the meridian about the last of June, and the first of July. 

" And, near to Helice, effulgent rays 
Beam, Ariadne, from thy starry crown: 
Twenty and one her stars ; but eight alone 
Conspicuous; one doubtful, or to claim 
The second order, or accept the third." 

HISTORY. 

This beautiful little cluster of stars is said to be in commemoration of a crown pre- 
sented by Bacchus to Ariadne, the daughter of Minos, second king of Crete. Theseus, 
king of Athens (1235 B. C), was shut up in the celebrated labyrinth of Crete, to be 
devoured by the ferocious Minotaur which was confined in that place, and which usually 
fed upon the chosen young men and maidens exacted from the Athenians as a yearly 
tribute to the tyranny of Minos ; but Theseus slew the monster, and being furnished with 
a clew of thread by Ariadne, who was passionately enamored of him, he extricated 
himself from the difficult windings of his confinement. 

He afterward married the beautiful Ariadne according to promise, and carried her 
away ; but when he arrived at the island of Naxos, he deserted her, notwithstanding he 
had received from her the most honorable evidence of attachment and endearing tender- 
ness. Ariadne was so disconsolate upon being abandoned by Theseus, that, as some say, 
she hanged herself; but Plutarch says that she lived many years after, and was espoused 
to Bacchus, who loved her with much tenderness, and gave her a crown of seven stars 
which, after her death, was placed among the stars. 

" Resolves, for this the dear engaging dame 

Should shine forever in the rolls of fame ; 

And bids her crown among the stars be placed, 

And with an eternal constellation graced. 

The golden circlet mounts ; and, as it flies, 

Its diamonds twinkle in the distant skies ; 

There, in their pristine form, the gemmy rays 

Between Alcides and the Dragon blaze." 
Manilius, in the first book of his Astronomicon, thus speaks of the Crown. 
" Near to Bootes the bright crown is view'd, 

And shines with stars of different magnitude: 

Or placed in front above the rest displays 

A vigorous light, and darts surprising rays. 

This shone, since Theseus first his faith betray'd, 

The monument of the forsaken maid." 

TELESCOPIC OBJECTS. 

1. a Corona Borealis (Alphaeca) — A bright star with a distant companion ; R. A. 
15h. 27m. 64s. ; Dec. N. 27° 15' 2". A 2, brilliant white ; B 8, pale violet. 

2. y Corona Borealis — A most difficult binary star, 2J^° from Alphaeca; R. A. 15h. 
86m. 01s. ; Dec. N. 26° 48' 4"; with a distant companion. A 6, flushed white ; B, uncer- 
tain ; C 10, pale lilac. 

3. C, Corosle Borealis — A fine double star, 10° north and a little easterly from Alphaeca ; 
R. A. 15h. 33m. 21s. ; Dec. N. 37° 09' 6". A 5, bluish white ; B 6, smalt blue. A beauti- 
ful object. 

4. T} CORON2B Borealis — A binary star, midway between the Northern Crown and the 
club of Bootes ; R. A. 15h. 16m. 36s. ; Dec. N. 30° 52' 2". A north-northwest ray from a 
Coronae, through j3, and half as far again, will hit it. A 6, white ; B 6Jg, golden yellow. 

188. How many stars in this constellation? Their magnitudes? Mean declination 
and right ascension ? 
History. — Story respecting Theseus and Ariadne ? 
Telescopic Objects. — Alpha? Gamma? Zeta? Eta? 



96 ASTRONOMY. 

Sir John Herschel considered this the most remarkable binary star known, and the only 
one that had completed a whole revolution since its discovery. Estimated period 432 
years. 



LtRSA MINOR (the lesser bear).— MAP VI. 

189. This constellation, though not remarkable in its appear 
ance, and containing but few conspicuous stars, is, nevertheless, 
justly distinguished from all others for the peculiar advantage, 
which its position in the heavens is well known to afford to nau- 
tical astronomy, and especially to navigation and surveying. 

The stars in this group being situated near the celestial pole, 
appear to revolve about it, very slowly, and in circles so small 
as never to descend below the horizon. Hence Ursa Minor will 
be above or below, to the right or left of the pole star, accord- 
ing to the hour ; as he makes the entire circuit from east to west 
every 24 hours. 

190. In all ages of the world, this constellation has been more 
universally observed, and more carefully noticed than any other, 
on account of the importance which mankind early attached to 
the position of its principal star. This star, which is so near the 
true pole of the heavens, has from time immemorial been deno- 
minated the North Polar Star. By the Greeks it is called 
Cynosyrc ; by the Romans, Cynosura, and by other nations, 
Alruccabah. In most modern treatises it bears the name of Po- 
laris, or Alpha Polaris. 

191 Polaris is of the 3d magnitude, or between the 2d and 
3d, and situated a little more than a degree and a half from the 
true pole of the heavens, on that side of it which is toward Cas- 
siopeia and opposite to Ursa Major. Its position is pointed out 
by the direction of the two Pointers, Merak and Dubhe, which 
lie in the square of Ursa Major. A line joining Beta Cassio- 
peia, which lies at the distance of 32° on one side, and Megrez, 
which lies at the same distance on the other, will pass through 
the polar star. 

Of the Pole Star Capt. Smyth observes : At present it is only 1° 33' from the polar point, 
and by its northerly precession in declination will gradually approach to within 26' 30" 
of it. This proximity to the actual pole will occur in A. D. 2095, but will not recur for 
12,860 years. The period of the revolution of the celestial equinoctial pole about the 
pole of the ecliptic, is nearly 26,000 years ; the north celestial pole, therefore, will be 
about 13,000 years ; hence, nearly 49° from the present polar star. 



189. For what is Ursa Minor distinguished? What said of its situation and Change of 
position? 190. What said of the notice taken of it? Position of its principal star? 
Its Greek and Latin names, &c. ? 191. Describe Polaris? How found? Remarks of 
Capt. Smyth respecting? 



URSA MINOR. 97 

192. So general is the popular notion, that the North Polar 
Star is the true pole of the world, that even surveyors and navi- 
gators, who have acquired considerable dexterity in the use of 
the compass and the quadrant, are not aware that it ever had 
any deviation, and consequently never make allowance for any. 
All calculations derived from the observed position of this star, 
which are founded upon the idea that its bearing is always due 
north of any place, are necessarily erroneous, since it is in this 
position only twice in twenty-four hours ; once when above, and 
once when below the pole. 

193. Hence, it is evident that the surveyor who regulates his 
compass by the North Polar Star, must take his observation 
when the star is on the meridian, either above or below the pole, 
or make allowance for its altered position in every other situa- 
tion. For the same reason must the navigator, who applies his 
quadrant to this star for the purpose of determining the latitude 
he is in, make a similar allowance, according as its altitude is 
greater or less than the true pole of the heavens ; for we have 
seen that it is alternately half the time above and half the time 
below the pole. 

194. The method of finding the latitude of a place from the 
altitude of the polar star, as it is very simple, is very often 
resorted to. Indeed, in northern latitudes, the situation of this 
star is more favorable for this purpose than that of any other of 
the heavenly bodies, because a single observation, taken at any 
hour of the night with a good instrument, will give the true lati- 
tude, without any calculation or correction, except that of its 
polar aberration. 

If the polar star always occupied that point in the heavens which is directly opposite 
the north pole of the earth, it would be easy to understand how latitude could be deter- 
mined from it in the northern hemisphere; for in this case, to a person on the equator, 
the poles of the world would be seen in the horizon. Consequently, the star would 
appear just visible in the northern horizon, without any elevation. Should the person 
now travel one degree toward the north, he would see one degree below the star, and he 
would think it had risen one degree. 

And since we always see the whole of the upper hemisphere at one view, when there 
is nothing in the horizon to obstruct our vision, it follows that if we should travel 10° 
north of the equator, we should see just 10° below the pole, which would then appear to 
have risen 10° ; and should we stop in the 42d degree of north latitude we should, in like 
manner, have our horizon just 42° below the pole, or the pole would appear to have an 
elevation of 42°. Whence we derive this general truth : The elevation of the pole of the 
equator is always equal to the latitude of the place of observation. 

Any instrument, then, which will give us the altitude of the north pole, wili give us 
also the latitude of the place. 

The method of illustrating this phenomenon, is given in most treatises on the globe, 

192. What popular error ? 193. When is the pole star a safe guide for the surveyor 
or mariner? What allowances should be made by each? 194. What said of finding 
the latitude by observations upon the pole star? What general rule stated? Wha 4 
error committed ? 



98 ASTRONOMY. 

and as adopted by teachers generally, is to tell the scholar that the north pole rises 
higher and higher, as he travels farther and farther toward it. In other words, what- 
ever number of degrees he advances toward the north pole, so many degrees will it rise 
above his horizon. This is not only an .obvious error in principle, but it misleads the 
apprehension of the pupil. It is not that the pole is elevated, but that our horizon is 
depressed as we advance toward the north. The same objection lies against the artifi- 
cial globe ; for it ought to be so fixed that the horizon might be raised or depressed, and 
the pole remain in its own invariable position. 

195. Ursa Minor contains twenty-four stars, including three 
of the 3d magnitude and four of the 4th. The seven principal 
stars are so situated as to form a figure very much resembling 
that in the Great Bear, only that the Dipper is reversed, and 
about one half as large as the one in that constellation. 

196. The first star in the handle, called Polaris, is the polar 
star, around which the rest constantly revolve. The two last in 
the bowl of the Dipper, corresponding to the Pointers in the 
Great Bear, are of the 3d magnitude, and situated about 15° 
from the pole. The brightest of them is called Kochab, which 
signifies an axle or hinge, probably in reference to its moving so 
near the axis of the earth. 

Kochab may be easily known by its being the brightest and middle one of the three 
conspicuous stars forming a row, one of which is about 2°, and the other 3° from Kochab. 
The two brighest of these are situated in the breast and shoulder of the animal, about 
3° apart, and are called the Guards or Pointers of Ursa Minor. They are on the meri- 
dian about the 20th of June, but may be seen at all hours of the night, when the sky ia 
clear. 

197. Of the four stars which form the bowl of the Dipper, 
one is so small as hardly to be seen. They lie in a direction 
toward Gamma in Cepheus ; but as they are continually chang- 
ing their position in the heavens, they may be much better traced 
out from the map, than from description. 

Kochab is about 25° distant from Benetnasch, and about 24° 
from Dubhe, and hence forms with them a very nearly equi- 
lateral triangle. 

« The Lesser Bear 

Leads from the pole the lucid band : the stars 
Which form this constellation, faintly shine, 
Twice twelve in number ; only one beams forth 
Conspicuous in high splendor, named by Greece 
The Cynoswe; by us, the Polar Stab." 

HISTORY. 

The prevailing opinion is that Ursa Major and Ursa Minor are the nymph Calisto and 
her son Areas, and that they were transformed into bears by the enraged and imperious 
Juno, and afterward translated to heaven by the favor of Jupiter, lest they might be 
destroyed by the huntsmen. 

The Chinese claim that the emperor Hong-ti, the grandson of Noah, first discoveied 



195. Number of stars in Ursa Minor ? Their magnitudes ? How situated ? 196. De- 
scribe Polaris, Kochab, and the Guards or Pointers? 197. Are all the stars distinctly 
visible? Direction? What triangle ? io ■ , . i„ij„.« r^nks? 

History.— What prevailing opinion, or myth ? Chinese claim ? Phemcians ? Ui eeks ( 



URSA MINOR. 99 

the polar star, and applied it to purposes of navigation. It is certain that it was used 
for this purpose in a very remote period of antiquity. From various passages in the 
ancients, it is manifest that the Phenicians steered by Cynosura, or the Lesser Bear; 
whereas, the mariners of Greece, and some other nations, steered by the Greater Bear, 
called Helice, or Helix. , 

Lucan, a Latin poet, who flourished about the time of the birth of our Saviour, thus 
adverts to the practice of steering vessels by Cynosura :— 

" Unstable Tyre now knit to firmer ground, 
With Sidon for her purple shells renown'd, 
Safe in the Cynosure their glittering guide 
With well-directed navies stem the tide." 

Rowe's Translation, B. iii. 

The following extracts from other poets contain allusions to the same fact: 

" Phenicia, spurning Asia's bounding strand, 
By the bright Pole star's steady radiance led, 
Bade to the winds her daring sails expand, 
And fearless plough'd old Ocean's stormy bed." 

Maurice's Elegy on Sir W. Jones. 

" Ye radiant signs, who, from the ethereal plain 
Sidonians guide, and Greeks upon the main, 
Who from your poles all earthly things explore, 
And never set beneath the western shore." 
Ovid's Tristia. 

" Of all yon multitude of golden stars, 
Which the wide rounding sphere incessant bears. 
The cautious mariner relies on none, 
But keeps him to the constant pole alone." 

Lucan's Pharsalia, B. viii. v. 225. 

Ursa Major and Ursa Minor are sometimes called Triones, and sometimes the Greater 
and Lesser Wains. In Pennington's Memoirs of the learned Mrs. Carter, we have the 
following beautiful lines :— 

"Here Cassiopeia fills a lucid throne, 
There, blaze the splendors of the Northern Crown ; 
While the slow Car, the cold Triones roll 
O'er the pale countries of the frozen pole : 
Whose faithful beams conduct the wandering ship 
Through the wide desert of the pathless deep." 
Thales, an eminent geometrician and astronomer, and one of the seven wise men of 
Greece, who flourished six hundred years before the Christian era, is generally reputed 
to be the inventor of this constellation, and to have taught the use of it to the Phenician 
navigators ; it is certain that he brought the knowledge of it with him from Phenice into 
Greece, with many other discoveries both in astronomy and mathematics. 

Until the properties of the magnet were known and applied to the use of navigation, 
and for along time after, the north polar star was the only sure guide. At what time the 
attractive powers of the magnet were first known, is not certain ; they were known in 
Europe about six hundred years before the Christian era ; and by the Chinese records, it 
is said that its polar attraction was known in that country at least one thousand years 
earlier. 

TELESCOPIC OBJECTS. 

1. a Ursje Minoris (Polaris)— A double star ; R. A. lh. 2m. 10s. ; Bee. N. 88" 27' 4". 
A 2>$, topaz yellow ;B9^, pale white. Map VIII., Fig. 12. 

2. j3 UrSjE Minoris (Kochab) — A star with a distant companion in the left shoulder ; 
R. A. 14h. 51m. 14s. ; Dec. N. 74° 48' 2". A 3, reddish ; B 11, pale grey— several small 
stars in the field. 

3. 6 Urs^e Mikoris— A star with a very distant telescopic companion in the middle of 
the tail of the figure ; R. A. 18h. 23m. 563. ; Dec. N. 86° 35' 4*. A 3, greenish tinge ; 
B 12, grey. 

What proofs from the poets ? What other names for Ursa Major and Ursa Minor ? Wh&t 
said of Thales ? Use of the pole star? The magnet? 
Tklescopic Objects.— Alpha ? Show on the map, Beta— Delta— Epsilon— Zeta, 

B.°r. 5 



]00 ASTRONOMY. 

4. e UrSjE Minoris — A star with a minute companion, at the root of the tail ; R. A. 
17h. 02m. 37s.; Dec. N. 82° 17' 01". A 4, bright yellow; B 12, pale blue; three other 
telescopic stars in the field. It is easily found, being the third star from Polaris. 

5. C Urs^e Minoris — A double star in the middle of the body ; R. A. 15h. 49m. 52s. ; 
Dec. N. 78° 16' 07". A 4, flushed white; B 11, bluish- with a yellow star of the 9th mag- 
nitude in the field. 



CHAPTER IX. 

CONSTELLATIONS ON THE MERIDIAN IN JULY. 

SCORPIO (the scorpion).— MAP Y. 

198. This is the eighth sign, and ninth constellation, in the 
order of the Zodiac. It presents one of the most interesting 
groups of stars for the pupil to trace out that is to be found in 
the southern hemisphere. It is situated southward and east- 
ward of Libra, and is on the meridian the 10th of July. 

The sun enters this sign on the 23d of October, but does not reach the constellation 
before the 20th of November. When astronomy was first cultivated in the East, the two 
solstices and the two equinoxes took place when the sun was in Aquarius and Leo, Tau- 
rus and Scorpio, respectively. 

199. Scorpio contains, according to Flamsted, forty-four stars, 
including one of the 1st magnitude, one of the 2d, and eleven of 
the 3d. It is readily distinguished from all others by the pecu- 
liar luster and the position of its principal stars. 

Antares is the principal star, and is situated in the heart of 
the Scorpion, about 19° east of Zubenelgubi, the southernmost 
star in the Balance. Antares is the most brilliant star in that 
region of the skies, and may be otherwise distinguished by its 
remarkably red appearance. Its declination is about 26° S. 
It comes to the meridian about three hours after Spica Yirginis, 
or fifty minutes after Corona Borealis, on the 10th of July. It 
is one of the stars from which the moon's distance is reckoned 
for computing the longitude at sea. 

There are four great stars in the heavens, Fomalhaut, Aldebaran, Begulus, and 
Antares, which formerly answered to the solstitial and equinoctial points, and which 
were much noticed by the astronomers of the East. 

200. About 8-J° northwest of Antares, is a star of the 2d 

198. Order of Scorpio among the signs, &c. ? Its comparative interest? Situation? 
When does the sun enter this sign ? When the constellation ? How with the solstices 
and equinoxes anciently? Why not so now? 199. Number and magnitudes of the 
stars in Scorpio ? How distinguished ? Name and position of its principal star ? How 
known ? What use made of it ? What three other stars mentioned ? 200. What other 



SCORPIO. 101 

magnitude, in the head of the Scorpion, called Graffias. It is 
but one degree north of the earth's orbit. It may be recognized 
by means of a small star, situated about a degree northeast of 
it, and also by its forming a slight curve with two other stars 
of the 3d magnitude, situated below it, each about 3° apart. 
The broad part of the constellation near Graffias, is powdered 
with numerous small stars, converging down to a point at 
Antares, and resembling in figure a boy's kite. 

201. As you proceed from Antares, there are ten conspicuous 
stars, chiefly of the 3d magnitude, which mark the tail of the 
kite, extending down, first in a south-southeasterly direction 
about 17°, thence easterly about 8° further, when they turn, 
and advance about 8° toward the north, forming a curve like a 
shepherd's crook, or the bottom part of the letter S. This 
crooked line of stars, forming the tail of the Scorpion, is very 
conspicuous, and may be easily traced. 

The first star below Antares, which is the last in the back, is of only the 4th magni- 
tude. It is about 2° southeast of Antares, and is denoted by the Greek name of T. 

EpsUon, of the 3d magnitude, is the second star from Antares, and the first in the 
tail It is situated about 7° below the star T, but inclining a little to the east. 

Mu, of the 3d magnitude, is the 3d star from Antares. It is situated 4%° below Epsi- 
lon. It may otherwise be known by means of a small star close by it, on the left. 

Zeta, of about the same magnitude, and situated about as far below Mu, is the fourth 
star from Antares. Here the line turns suddenly to the east. 

Ma, also of the 3d magnitude, is the fifth star from Antares, and about 336° east of 
Zeta. 

Theta, of the same magnitude, is the sixth star from Antares, and about 4^° east 
of Eta. Here, the line turns again, curving to the north, and terminates in a couple 
of stars. 

lota is the seventh star from Antares, 3H' above Theta, curving a little to the left. 
It is a star of the 3d magnitude, and may be known by means of a small star, almost 
touching it, on the east. 

Kappa, a star of equal brightness, is less than 2° above Iota, and a little to the right. 

Lesuth, of the 3d magnitude, is the brightest of the two last, in the tail, and is situated 
about 3° above Kappa, still further to the right. It may readily be known by means of 
a smaller star, close by it, on the west. 

202. This is a very beautiful group of stars, and easily traced 
out in the heavens. It furnishes striking evidence of the facility 
with which most of the constellations may be so accurately 
delineated, as to preclude everything like uncertainty in the 
knowledge of their relative situation. 

" The heart with luster of amazing force, 
Refulgent vibrates ; faint the other parts, 
And ill-defined by stars of meaner note." 

HISTORY. 

This sign was anciently represented by various symbols, sometimes by a snake, and 
sometimes by a crocodile ; but most commonly by the scorpion. This last symbol is 



star described ? Size and position ? How recognized ? What said of the broad part or 
body of Scorpio ? 201. What stars form the tail of Scorpio? Are they conspicuous ? 
Name and describe in detail? 202. General remarks respecting this constellation? 
History. — How was Scorpio anciently delineated ? How regarded by ancient astrolo- 



102 ASTRONOMY. 

found on the Mithraic monuments, which is pretty good evidence that these monuments 
were constructed when the vernal equinox accorded with Taurus. 

On both the zodiacs of Dendera, there are rude delineations of this animal ; that on 
the portico differs considerably from that on the other zodiac, now in the Louvre. 

Scorpio was considered by the ancient astrologers as a sign accursed. The Egyptians 
fixed the entrance of the sun into Scorpio as the commencement of the reign of Typhon, 
when the Greeks fabled the death of Orion. When the sun was in Scorpio, in the month 
of Athyr, as Plutarch informs us, the Egyptians inclosed the body of their god Osiris in 
an ark, or chest, and during this oeremony a great annual festival was celebrated. 
Three days after the priests had inclosed Osiris in the ark, they pretended to have found 
him again. The death of Osiris, then, was lamented when the sun in Scorpio descended 
to the lower hemisphere, and when he arose at the vernal equinox, then Osiris was said 
to be born anew. 

The Egyptians or Chaldeans, who first arranged the Zodiac, might have placed Scorpio 
in this part of the heavens to denote that when the sun enters this sign, the diseases 
incident to the fruit season would prevail ; since Autumn, which abounded in fruit, often 
brought with it a great variety of diseases, and might be thus fitly represented by that 
venomous animal, the scorpion, who, as he recedes, wounds with a sting in his tail. 

Mars was the tutelary deity of the Scorpion, and to this circumstance is owing all that 
jargon of the astrologers, who say that there is a great analogy between the malign 
influence of the planet Mars and this sign. To this also is owing the doctrine of the 
alchemists, that iron, which metal they call Mars, is under the dominion of Scorpio ; so 
that the transmutation of it into gold can be effected only when the sun is in this sign. 

The constellation of the Scorpion is very ancient. Ovid thus mentions it in his beau- 
tiful fable of Phaeton : — 

" There is a place above, where Scorpio bent, 
In tail and arms surrounds a vast extent ; 
In a wide circuit of the heavens he shines, 
And fills the place of two celestial signs.'' 

According to Ovid, this is the famous scorpion which sprang out of the earth at the 
command of Juno, and stung Orion ; of which wound he died. It was in this way the 
imperious goddess chose to punish the vanity of the hero and the hunter, for boasting 
that there was not on earth any animal which he could not conquer. 

" Words that provoked the gods once from him fell, 
'No beasts so fierce,' said he, 'but I can quell;' 
When lo ! the earth a baleful scorpion sent, 
To kill Latona was the dire intent ; 
Orion saved her, though himself was slain, 
But did for that a spacious place obtain 
In heaven : ' to thee my life? said she, '■was dear, 
And for thy merit shine illustrious there." 

Although both Orion and Scorpio were honored by the celestials with a place among 
the stars, yet their situations were so ordered that when one rose the other should set, 
and vice versa; so that they never appear in the same hemisphere at the same time. 

In the Hebrew^odiac this sign is allotted to Dan, because it is written, " Dan shall be 
a serpent by the way, an adder in the path." 

TELESCOPIC OBJECTS. 

!• a Scorpii (Antares) — A bright star with a companion in the heart of Scorpio ; R. A 
16h. 19m. 36s. ; Dec. S. 26° 04' 3°. A 1, fiery red ; B 8, pale. Very close. 

2. (3 Scorpii (Graffias) — A star with a companion in the head; R. A. 15h. 56m. 08s.; 
Dec. S. 19° 21' 7". A 2, pale white ; B 5%, lilac tinge. 

8. v Scorpii — A neat double star, east by north from (3 about 2° ; R. A. 16h. 02m. 42s. ; 
Dec. S. 19° 02' 3". A 4, bright white ; B 7, pale lilac. Professor Mitchell registers this 
»s a triple star. 

4. a Scorpii— A delicate double star in the body of the figure ; R. A. 16h. 11m. 28s. ; 

gers ? Egyptian myth respecting Typhon, &c. ? Supposed reason why Scorpio was placed 
where it is? Why do astrologers connect Mars with Scorpio ? The Alchemists? What 
poetic proof of the antiquity of Scorpio ? Ovid's myth respecting ? Relative position of 
Orion and Scorpio ? Place of Scorpio in the Hebrew Zodiac, and why ? 

Telescopic Objects.— Alpha? Beta? Nu? Sigma? What cluster? Point out on the 
map. What Nebula ? 



HERCULES. 103 

Dec. S. 26° 12' 2". About 2° west by north of Antares. A 4, creamy white; B 9H 
lilac tint. 

5. A compressed globular cldster in the right foot of Ophiuchus, or the Scorpion's 
back ; R. A. 16h. 07m. 28s. ; Dec. S. 22° 35' 4". Half way between a and /? Scorpii, or 4° 
east of 6. A fine bright object, in an open space, with a few telescopic stars in the 
field. Pronounced by Herschel " the richest and most condensed mass of stars which 
the firmament can offer to the contemplation of astronomers." Map IX., Tig. 52. 

6. A compressed mass of very small stars, in the middle of the body, with outlayers, 
and a few stellar companions in the field ; R. A. 16h. 13m. 51s. ; Dec. S. 26° 07' 5°. It is 
1%° west of Antares. Elongated and bright in the center. 

7. A fine large resolvable nebula at the root of the tail, about 7° southeast from 
Antares ; R. A. I6h. 51m. 04s. ; Dec. S. 29° 50' 6". A mass of small stars running up to a 
blaze in the center — has been mistaken for a comet. 



HEEOULES.— MAP Y. 

203. Hercules is represented on the map invested with the 
skin of the Nemsean Lion, holding a massy club in his right 
hand, and the three-headed dog Cerberus in his left. He occu- 
pies a large space in the northern hemisphere, with one foot rest- 
ing on the head of Draco, on the north, and his head nearly 
touching that of Ophiuchus, on the south. This constellation 
extends from 12° to 50° north declination, and its mean right 
ascension is 255° ; consequently its centre is on the meridian 
about the 21st of July. 

204. Hercules is bounded by Draco on the north, Lyra on the 
east, Ophiuchus or the Serpent-Bearer on the south, and the Ser- 
pent and the Crown on the west. It contains one hundred and 
thirteen stars, including one of the 2d, or of between the 2d and 
3d magnitudes, nine of the 3d magnitude, and nineteen of the 
4th. The principal star is Ras Algethi, and is situated in the 
head, about 25° southeast of Corona Borealis. It may be 
readily known by means of another bright star of .equal magni- 
tude, 5° east-southeast of it, called Ras Alhague. Has Alhague 
marks the head of Ophiuchus, and Has Algethi that of Her- 
cules. These two stars are always seen together like the bright 
pairs in Aries, Gemini, the Little Dog, &c. They come to our 
meridian about the 28th of July, near where the sun does the 
last of April, or the middle of August. 

About midway between Ras Algethi on the southeast, and Ariadne's Crown on the 
northwest, may be seen Beta and Gamma, two stars of the 3d magnitude, situated in 
the west shoulder, about 3° apart. The northernmost of these two is called ButiUcus. 

Those four stars in the shape of a diamond, 8° or 10* southwest of the two in the 
shoulder of Hercules, are situated in the head of the Serpent. 



203. Describe Hercules? His magnitude and position? When on the meridian? 
204. How bounded? Number of stars ? Their size? Principal star, and how known ? 
What said of Ras Alhague, and Ras Algethi ? Of Beta and Gamma ? 



1 04 ASTRONOMY. 

205. About 12° E. N. E. of Rutilicus, and 10^° directly north ol 
Ras Algethi, are two stars of the 4th magnitude, in the east 
shoulder. They may be known by two very minute stars a little 
above them on the left. The two stars in each shoulder of Her- 
cules, with Ras Algethi in the head, form a regular triangle. 

The left, or east arm of Hercules, which grasps the triple-headed monster Cerberus, 
may be traced by means of three or four stars of the 4th magnitude, situated in a row, 
3° and 4° apart, extending from the shoulder, in a northeasterly direction. That small 
cluster, situated in a triangular form, about 14° northeast of Ras Algethi, and 13" east- 
southeast of the left shoulder, distinguish the head of Cerberus. 

Eighteen or 20° northeast of the Crown, are four stars of the 3d and 4th magnitudes, 
forming an irregular square, of which the two southern ones are about 4" apart, and in 
a line 6° or 7° south of the two northern ones, which are nearly 7° apart. 

Pi, in the northeast corner, may be known by means of one or two other small stars, 
close by it, on the east. Eta, in the northwest corner, may be known by its being in a 
row with two smaller stars, extending toward the northwest, and about 4° apart. The 
stars of the 4th magnitude, just south of the Dragon's head, point out the left foot and 
ankle of Hercules. 

Several other stars, of the 3d and 4th magnitudes, may be traced out in this constella- 
tion, by reference to the map. 

HISTORY. 

This constellation is intended to immortalize the name of Hercules, the Theban, so 
celebrated in antiquity for his heroic valor and invincible prowess. According to the 
ancients, there were many persons of this name. Of all these, the son of Jupiter and 
Alcmena is the most celebrated, and to him the actions of the others have been gene- 
rally attributed. 

The birth of Hercules was attended with many miraculous events. He was brought 
up at Tirynthus, or at Thebes, and before he had completed his eighth month, the jealousy 
of Juno, who was intent upon his destruction, sent two snakes to devour him. Not ter- 
rified at the sight of the serpents, he boldly seized them, and squeezed them to death, 
while his brother Iphicles alarmed the house with his frightful shrieks. 

He was early instructed in the liberal arts, and soon became the pupil of the centaur 
Chiron, under whom he rendered himself the most valiant and accomplished of all the 
heroes of antiquity. In the 18th year of his age, he commenced his arduous and glorious 
pursuits. He subdued a, lion that devoured the flocks of his supposed father, Amphi- 
tryon. After he had destroyed the lion, he delivered his country from the annual tri- 
bute of a hundred oxen, which it paid to Eiginus. 

As Hercules, by the will of Jupiter, was subjected to the power of Eurystheus, and 
obliged to obey him in every respect, Eurystheus, jealous of his rising fame and power, 
ordered him to appear at Mycenae, and perform the labors which, by priority of birth, 
he was empowered to impose upon him. Hercules refused, but afterwards consulted 
the oracle of Apollo, and was told that he must be subservient, for twelve years, to the 
will of Eurystheus, in compliance with the commands of Jupiter ; and that, after he had 
achieved the most celebrated labors, he should be reckoned in the number of the gods. 
So plain an answer determined him to go to Mycenae, and to bear with fortitude what- 
ever gods or men should impose upon him. Eurystheus, seeing so great a man totally 
subjected to him, and apprehensive of so powerful an enemy, commanded him to achieve 
a number of enterprises the most difficult and arduous ever known, generally called the 
Twelve Labors of Hercoles. Being furnished with complete armor by the favor of the 
gods, he boldly encountered the imposed labors. 

1. He subdued the Nemaean Lion in his den, and invested himself with his skin. 

2. He destroyed the Lernaean Hydra, with a hundred hissing heads, and dipped his 
arrows in the gall of the monster, to render their wounds incurable. 

3. He took alive the stag with golden horns and brazen feet, so famous for its incre- 
dible swiftness, after pursuing it for twelve months, and presented it, unhurt, to 
Eurystheus. 

4. He took alive, the Erymanthian Boar, and killed the Centaurs who opposed him. 

205. What two other stars, and what triangle? How trace the left or east arm of Her- 
cules? What four stars, and forming what? Describe Pi, and how known. Eta? Any 
other stars ? 

History. — Design of this constellation ? Story of the birth of Hercules ? His wonderful 



HERCULES. 105 

5. He cleansed the stables of Augias, in which 3,000 oxen had been confined for many 
years. 

6. He killed the carnivorous birds which ravaged the country of Arcadia, and fed on 
human flesh. 

7. He took alive, and brought into Peloponnesus, the wild bull of Crete, which no 
mortal durst look upon. 

S. He obtained for Eurystheus the mares of Diomedes, which fed on human flesh after 
having given then - owner to be first eaten by them. 

9. He obtained the girdle of the queen of the Amazons, a formidable nation of warlike 
females. 

10. He killed the monster G-eryon, king of Gades, and brought away his numerous 
flocks, which fed upon human flesh. 

11. He obtained the golden apples from the garden of the Hesperides, which were 
watched by a dragon. 

12. And finally, he brought up to the earth the three-headed dog Cerberus, the guar- 
dian of the entrance to the infernal regions. 

According-to Dupuis, the twelve labors of Hercules are only a figurative representation 
of the annual course of the sun through the twelve signs of the Zodiac ; Hercules being put 
for the sun, inasmuch as it is the powerful planet which animates and imparts fecundity 
to the universe, and whose divinity has been honored, in every quarter, by temples and 
altars, and consecrated in the religious strains of all nations. 

Thus Virgil, in the eighth book of his JEneid, records the deeds of Hercules, and cele- 
brates his praise .— 

" The lay records the labors, and the praise, 

And all the immortal acts of Hercules. 

First, how the mighty babe, when swath'd in hands, 

The serpents strangled with his infant hands ; 

Then, as in years and matchless force he grew, 

The (Echalian walls and Trojan overthrew, 

Besides a thousand hazards they relate, 

Procured by Juno's and Eurystheus' hate. 

Thy hands, unconquer'd hero, could subdue 

The cloud-born Centaur, and the monster crew; 

Nor thy resistless arm the bull withstood; 

Nor he, the roaring terror of the wood. 

The triple porter of the Stygian seat 

With lolling tongue lay fawning at thy feet, 

And, seized with fear, forgot the mangled meat. 

The infernal waters trembled at thy sight: 

Thee, god, no face of danger could affright; 

Nor huge Typhasus, nor the unnumber'd snake, 

Increased with hissing heads, in Lerna's lake." 

Besides these arduous labors which the jealousy of Eurystheus imposed upon him, he 
also achieved others of his own accord, equally celebrated. Before he delivered himself 
up to the king of Mycenae he accompanied the Argonauts to Colchis. He assisted the 
gods in their wars against the giants, and it was through him alone that Jupiter obtained 
the victory. He conquered Laomedon and pillaged Troy. 

At three different times he experienced fits of insanity. In the second, he slew the 
brother of his beloved Iole ; in the third he attempted to carry away the sacred tripod 
from Apollo's temple at Delphi, for which the oracle told him he must be sold as a slave. 
He was sold accordingly to Omphale, queen of Lydia, who restored him to liberty, and 
married him. After this he returned to Peloponnesus, and re-established on the throne 
of Sparta his friend Tyndarus, who had been expelled by Hippocoon. He became 
enamored of Dejanira, whom, after having overcome all his rivals, he married ; but was 
obliged to leave his father-in-law's kingdom, because he had inadvertently killed a man 
with a blow of his fist. He retired to the court of Ceyx, king of Trachina, and in his 
way was stopped by the streams of the Evenus, where he slew the Centaur Xessus, for 
presuming to offer indignity to his beloved Dejanira. The Centaur, on expiring, gave to 
Dejanira the celebrated tunic which afterward caused the death of Hercules. "This 
tunic," said the expiring monster, " has the virtue to recall a husband from unlawful 
love." Dejanira, fearing lest Hercules should relapse again into love for the beautiful 
Iole, gave him the fatal tunic, which was so infected with the poison of the Lernaean 

exploits? Origin and character of the twelve labors? "What are these labors supposed 
to represent ? What quotation from Virgil ? Story of the death of Hercules ? Ovid ? 



106 ASTRONOMY. 

Hydra, that he had no sooner invested himself with it, than it began to penetrate his 
bones, and to boil through all his veins. He attempted to pull it off, but it was too late. 
" As the red iron hisses in the flood, 

So boils the venom in his curdling blood. 

Now with the greedy flame his entrails glow, 

And livid sweats down all his body flow ; 

The crackling nerves, burnt up, are burst in twain, 

The lurking venom melts his swimming brain." 

As the distemper was incurable, he implored the protection of Jupiter, gave his bow 
and arrows to Philoctetes, and erected a large burning pile on the top of Mount (Eta. 
He spread on the pile the skin of the Nemaean lion, and laid himself down upon it, as on 
a bed, leaning his head upon his club. Philoctetes set fire to the pile, and the hero saw 
himself, on a sudden, surrounded by the most appalling flames ; yet he did not betray 
any marks of fear or astonishment. Jupiter saw him from heaven, and told the sur- 
rounding gods, who would have drenched the pile with tears, while they estreated that 
he would raise to the skies the immortal part of a hero who had cleared the earth from 
so many monsters and tyrants ; and thus the thunderer spake : — 

" Be all your fears forborne : 

The (Etean fires do thou, great hero, scorn. 

Who vanquish'd all things shall subdue the flame 

That part alone of gross maternal frame 

Fire shall devour ; while what from me he drew 

Shall live immortal, and its force subdue : 

That, when he's dead, I'll raise to realms above ; — 

May all the powers the righteous act approve." 

Ovid's Met. lib. ix. 
Accordingly, after the mortal part of Hercules was consumed, as the ancient poets 
say, he was carried up to heaven in a chariot drawn by four horses. 

" Quem pater omnipotens inter cava nubila raptum, 
Quadrijugo curru radiantibus intulit astris." 

'• " Almighty Jove 

In his swift, car his honor'd offspring drove ; 
High o'er th e hollow clouds the coursers fly, 
And lodge the hero in the starry sky." 

Ovid's Met. lib. ix. v. 271. 

TELESCOPIC OBJECTS. 

1. a Herculis (Ras Algethi) — A beautiful double star in the head of Hercules ; R. A. 
17h. 07m. 21s. ; Dec. N. 14° 34' 05". A 3%, orange ; B 5%, greenish. Map VIII., Pig. 13. 

2. j$ Herculis (Rutilicii*)—A fine double star in a barren field, on the hero's left 
shoulder; R. A. 16h. 23m. 21s. ; Dec. N. 21° 50' 6". A 2%, pale yellow; B 11, lilac tint. 

3. y Herculis — An open double star in a dark field, on the left arm; R. A. 16h. 14m. 
53s.; Dec. N. 19° 32' 0". A 3%, silvery white ; B10, lilac. About half-way from Ras 
Algethi, in the head, to Alphacca in the Northern Crown. 

4. J Herculis — A binary star on the right shoulder, and about 11° due north of a- 
R. A. 17h. 08m. 2Ss. ; Dec. N. 25° 01' 9". A 4, greenish white; B 8}£, grape red. It 
forms an equilateral triangle with a and ft. 

5. f Herculis — A close binary star over the middle of the body ; R. A. 16h. 35m. 15s. ; 
Dec. N. 31° 53' 7". A3, yellowish white; B 6, orange tint. A " wonderous object" — 
one star being sometimes occulted by the other. 

6. 7] Herculis — A bright star with a distant companion on the left thigh ; R. A. 16h. 
37m. 25s. ; Dec. N. 39° 13' 8". A 3, pale yellow ; B 10, dusky. 

7. A large cluster on the left thigh, between f and 77, 3}£° southwesterly of the 
latter; R. A. 16h. 35m. 58s. ; Dec. N. 36° 45' 8". A superb object, blazing up in the cen- 
ter, with numerous outlayers. Map IX., Fig. 53. May be seen by the naked eye in the 
absence of the moon. 

8. A globular cluster of minute stars 1%° north by east of rj ; R. A. 17h. 12m. 14s.; 
Dec. N. 43" 18' 4". Large, bright, and resolvable, with a luminous centre. Several 
other stars in the field. Map IX., Fig. 54. 

Telescopic Objects. — Alpha? Point out on the map Beta? Gramma? Delta? Zeta? 
Eta? What clusters? Point out on the map. What Nebula? 



SERPENTARIUS. 107 

9. A small planetary nebula between the hero's shoulders ; R. A. 16h. 37m. 46s. ; Dec. 
24° 05' 8". A curious object, with a disc 8" in diameter. Look northeast of y and j3 
in the left arm, to a point forming an equilateral triangle with these two stars. 

10. A fine planetary nebula near the right knee of Hercules; R. A. 16h. 43m. 23s. ; 
Dec. N. 46° 47' 0". About 4° east by north from T- It is large, round, and of a lucid 
pale blue hue. A 6th magnitude star near it somewhat eclipses its brightness. 



SERPENTAEIUS, YEL OPHH7CHUS (the serpent bearer).— 

map y. 

206. The Serpent-Bearer is also called iEsculapius, or the 
god of medicine. He is represented as a man with a venerable 
beard, having both hands clenched in the folds of a prodigious 
serpent, which is writhing in his grasp. 

The constellation occupies a considerable space in the mid- 
heaven, directly south of Hercules, and west of Taurus Ponia- 
towski. Its center is very nearly over the equator, opposite to 
Orion, and comes to the meridian the 26th of July. It contains 
seventy-four stars, including one of the 2d magnitude, five of 
the 3d, and ten of the 4th. 

207. The principal star in Serpentarius is called Ras Alhague. 
It is of the 2d magnitude, and situated in the head, about 5° 
E. S. E. of Ras Algethi, in the head of Hercules. Ras Alhague 
is nearly 13° N. of the equinoctial, while Rho, in the southern 
foot, is about 25° south of the equinoctial. These two stars 
serve to point out the extent of the constellation from north to 
south. Ras Alhague comes to the meridian on the 28th of July, 
about 21 minutes after Ras Algethi. 

About 10° S. W. of Ras Alhague are two small stars of the 4th magnitude, scarcely 
more than a degree apart. They distinguish the left or west shoulder. The northern 
one is marked Iota and the other Kappa. 

Eleven or twelve degrees S. S. E. of Ras Alhague are two other stars of the 3d magni- 
tude, in the east shoulder, and about 2° apart. The upper one is called Oheleo, and the 
lower one Gamma. These stars in the head and shoulders of Serpentarius, form a tri- 
angle, with the vertex in Ras Alhague, and pointing toward the northeast. 

208. About 4° E. of Gamma, is a remarkable cluster of four 
or five stars, in the form of the letter Y, with the open part to 
the north. It very much resembles the Hyades. This beautiful 
little group mark the face of Taurus Pontatowski. The solsti- 
tial colure passes through the equinoctial about 2° E. of the 

206. What other name has the Serpent Bearer? How represented? Situation and 
extent? Number and size of its principal stars? 207. Name of its principal star? 
Magnitude and situation? Rho, and its situation? Use of these two stars? What said 
of Iota and Kappa? Of Cheleb and Gamma? 208. What remarkable cluster? For 



5 



•H- 



108 ASTRONOMY. 

lower star in the vertex of the V. The letter name of this 
star is k. 

There is something remarkable in its central position. It is situated almost exactly tn 
the mid-heavens, being nearly equidistant from the poles, and midway between the ver- 
nal and autumnal equinoxes. It is, however, about one and a third degrees nearer the 
north than the south pole, and about two degrees nearer the autumnal than the vernal 
equinox, being about two degrees west of the solstitial colure. 

Directly south of the V, at the distance of about 12°, are two very small stars, about 
2° apart, situated in the right hand, where it grasps the serpent. About half-way 
between, and nearly in a line with, the two in the hand and the two in the shoulder, is 
another star of the 3d magnitude, marked Zeta, situated in the Serpent, opposite the 
right elbow. It may be known by means of a minute star just under it. 

Marsic, in the left arm, is a star of the 4th magnitude, about 10° S. W. of Iota and 
Kappa. About 7° farther in the same direction are two stars of the 3d magnitude, situ- 
ated in the hand, and a little more than a degree apart. The upper one of the two, 
which is about 16° N. of Gramas in Scorpio, is called Yed; the other is marked Epsilon. 
These two stars mark the other point in the folds of the monster where it is grasped by 
Serpentarius. 

The left arm of Serpentarius may be easily traced by means of the two stars in the 
shoulder, the one (Marsic) near the elbow, and the two in the hand; all lying nearly 
in a line N. .N. E. and S. S. W. In the same manner may the right arm be traced, by 
stars very similarly situated ; that is to say, first by the two in the east shoulder, just 
west of the V, thence 8° in a southerly direction inclining a little to the east, by Zeta, 
(known by a little star right under it,) and then by the two small ones in the right hand, 
situated about 6° below Zeta. 

About 12° from Antares, in an easterly direction, are two stars in the right foot, about 
2° apart. The largest and lower of the two, is on the left hand. It is of between the 
8d and 4th magnitudes, and marked Mho. There are several other stars in this constel- 
lation of the 3d and 4th magnitudes. They may be traced out from the maps. 

" Thee, Serpentarius, we behold distinct, 
With seventy-four refulgent stars ; and one 
Graces thy helmet, of the second class : 
The Serpent, in thy hand grasp'd, winds his spire 
Immense ; fewer by ten his figure trace ; 
One of the second rank ; ten shun the sight ; 
And seven, he who bears the monster hides." — Eudosia. 

HISTORY. 

This constellation was known to the ancients twelve hundred years before the Chris- 
tian era. Homer mentions it. It is thus referred to in the Astronomicon of Manilius : — 
" Next, Ophiuchus strides the mighty snake, 
Untwists his winding folds, and smooths his back, 
Extends his bulk, and o'er the slippery scale 
His wide-stretch'd hands on either side prevail 
The snake turns back his head and seems to rage : 
That war must last where equal power prevails." 

JEsculapius was the son of Apollo, by Coronis, and was educated by Chiron the Cen- 
taur in the art of medicine, in which he became so skilful, that he was considered the 
inventor and god of medicine. At the birth of JEsculapius, the inspired daughter of 
Chiron uttered, "in sounding verse," this prophetic strain. 

" Hail, great physician of the world, all hail ! 

Hail, mighty infant, who, in years to come, 

Shall heal the nations and defraud the tomb ! 

Swift be thy growth ! thy triumphs unconfined 1 

Make kingdoms thicker, and increase mankind : 

Thy daring art shall animate the dead, 

And draw the thunder on thy guilty head : 

Then shalt thou die, but from the dark abode 

Rise up victorious, and be twice a god." 

and resemblance? Marks what? What said of the lower star in the V. ? What stars 
south of it ? What of Marsic ? Of Yed and Epsilon ? How trace the left arm ? 

History. — Antiquity of this constellation ? Proof? Who was iEsculapius ? Account 
of his great skill ? His metamorphosis ? Remarkable fact respecting Socrates and Plato ? 



SERPENTARIUS. 109 

He accompanied the Argonauts to Colchis, in the capacity of physician. He is said to 
have restored many to life, insomuch that Pluto complained to Jupiter, that his dark 
dominion was in danger of being depopulated by his art. 

iEsculapius was worshiped at Epidaurus, a city of Peloponnesus, and hence he is 
styled by Milton " the god in Epidaurus." Being sent for to Rome in the time of a plague, 
he assumed the form of a serpent and accompanied the ambassadors, but though thus 
changed, he was iEsculapius still, in serpente deus — the deity in a serpent — and under 
that form he continued to be worshiped at Rome. The cock and the serpent were sacred 
to him, especially the latter. The ancient physicians used them in their prescriptions. 

One of the last acts of Socrates, who is accounted the wisest and best man of Pagan 
antiquity, was to offer a cock to iEsculapius. He and Plato were both idolaters ; they 
conformed, and advised others to conform, to the religion of their country ; to gross 
idolatry and absurd superstition. If the wisest and most learned were so blind, what 
must the foolish and ignorant have been ? 

TELESCOPIC OBJECTS. 

1. a Ophiuchi {Ras Alhague) — A bright star with a minute companion, in the head of 
the figure ; R. A. ITh. 27m. 30s. ; Dec. N. 12° 40' 08". A 2, sapphire ; B 9, pale grey. A 
coarse triplet of small stars near them. 

2. 6 Ophiuchi (Yed) — A star with a distant companion, in the right hand ; R. A. 16h. 
05m. 5Ss. ; Dec. S. 3° 16' 07". A 3, deep yellow; B 10, pale lilac ; a third minute star in 
the field. 

3. 7] Ophiuchi — A brilliant star with a distant companion, on the left knee ; on the 
margin of the milky way ; R. A. 17h. 01m. 13s. ; Dec. N. 15° 31' 03". A 233, pale yellow ; 
B 13, blue. 

4. T Ophiuchi — A close binary star on the left hand, 15° northeast of the bright star 
7}, just described, towards Altair; R. A. 17h. 54m. 22s.; Dec. S. 8° 10' 04". A 5, and B 
6, both pale white ; C 10, light blue ; two other stars in the field. Out of place on the 
map, or R. A. wrong in the tables, as given above. 

5. A triple or rather multiple star, between the left foot of Ophiuchus, and the root of 
the tail of Scorpio ; R. A. 17h. 05m. 29s. ; Dec. S. 26° 21' 05". It is about 10° due east of 
Antares. A 4%, ruddy; B 633, pale yellow; C 733, greyish. The latter is double, a 
minute companion appearing at a distance, though not seen through ordinary instruments. 
For relative position, &c, see Map VIII., Fig. 14. 

6. A fine globular cluster, between the right hip and elbow ; R. A. 16h. 88m. 56s. ; 
Dec. S. 1° 40' 03". A rich cluster, condensed towards the center, with many straggling 
outlayers. About 8° from £ Ophiuchi, towards /3. 

7. A rich cluster of compressed stars, in the right hip ; R. A. 16h. 48m. 45s. ; Dec. S. 
3° 51' 08". About 8° east of e Ophiuchi; or half-way between /3 Librae, and a Aquilae. A 
beautiful round cluster, and may be seen with a telescope three feet in length. 

8. A round cluster on the left leg ; R. A. 17h. 09m. 42s. ; Dec. S. 18° 20' 07'. It lies 
about 3° southeast of e, and rather more than 3£ the distance on a line from Antares to 
Altair. A fine object — myriads of stars clustering to a blaze in the center. 

9. A large globular cluster in the left arm ; R. A. 17h. 29m. 13s. ; Dec. S. 3° 09' 01*. 
It lies 16° south of Ras Alhague, or about half way from (3 Scorpii to £ Aquilae. 633° south- 
by-west of y Ophiuchi. A fine object, of a lucid white, and may be seen with small instru- 
ments. Several stars in the field. Map IX., Fig. 55. 

Telescopic Objects. — Alpha? Delta? Eta? What multiple star ? Point out on the 
map. What clusters ? Which shown on the map ? 



HO ASTRONOMY. 

CHAPTER X. 

CONSTELLATIONS ON THE MERIDIAN IN AUGUST. 

DRACO (the dragon).— MAP VI. 

209. This constellation, which compasses a large circuit in the 
polar regions by its ample folds and contortions, contains many- 
stars which may be easily traced. From the head of the mon- 
ster, which is under the foot of Hercules, there is a complete 
coil tending eastwardly, about 11° N. of Lyra ; thence he winds 
down northerly about 14° to the second coil, where he reaches 
almost to the girdle of Cepheus ; then he loops down somewhat 
in the shape of the letter U, and makes a third coil about 15° 
below the first. From the third coil he holds a westerly course 
for about 13°, then goes directly down, passing between the 
head of the Lesser and the tail of the Greater Bear. 

210. Draco contains eighty stars, including two of the 2d 
magnitude, three of the 3d, and sixteen of the 4th. 

" The Dragon next, winds like a mighty stream : 
Within its ample folds are eighty stars, 
Four of the second order. Far he waves 
His ample spires, involving either Bear." 

The head of the Dragon is readily distinguished by means of 
four stars, 3°, 4°, and 5° apart, so situated as to form an irregu- 
lar square ; the two upper ones being the brightest, and both 
of the 2d magnitude. The right-hand upper one, called Etanin, 
has been rendered very noted in modern astronomy from its 
connection with the discovery of a new law in physical science, 
called the Aberration of Light. 

The letter name of this star is Gamma, or Gamma Draconis ; and by this appellation 
it is most frequently called. The other bright star, about 4° from it on the left, is 
Rastaben. 

211. About 4° W. of Rastaben, a small star may, with close 
attention, be discerned in the nose of the Dragon, which, with 
the irregular square before mentioned, makes a figure somewhat 
resembling an Italic V, with the point toward the west, and the 
open part toward the east. The small star in the nose, is called 
Er Rakis. ■ 

209. Describe Draco — its situation and extent. 210. Number and size of its princi- 
pal stars ? How may the head of Draco be distinguished? What said of Etanin? Its 
letter name? What of Rastaben? 211. Of Er Rakis? Further of Rastaben? Of 
Etanin? Of Grumium 1 Of Omicron ? How may the second coil be recognized? What 
of Zeta ? Of Eta, Theta, and Asich ? Of Thuban, Kappa, and Giansar ? 



DRACO. Ill 

The two small stars 5* or 6° S. of Rastaben are in the left foot of Hercules. 

Rastaben is on the meridian nearly at the same moment with Ras Alhague. Etanin, 
40° N. of it, is on the meridian about the 4th of August, at the same time with the three 
western stars in the face of Taurus Poniatowskii, or the V. It is situated less than 2° west 
of the solstitial colure, and is exactly in the zenith of London. Its favorable position has 
led English astronomers to watch its appearance, for long periods, with the most exact and 
unwearied scrutiny. 

Of the four stars forming the irregular square in the head, the lower and right-hand one 
is 5%° N. of Etanin. It is called Grumium, and is of the 3d magnitude. A few degrees 
E. of the square, may be seen, with a little care, eight stars of the 5th magnitude, and one 
of the 4th, which is marked Omioron, and lies 8° E. of Grumium. This group is in the first 
coil of the Dragon. 

The second coil is about 13° below the first, and may be recognized by means of four 
stars of the 3d and 4th magnitudes, so situated as to form a small square, about half the 
size of that in the head. The brightest of them is on the left, and is marked Delta. A line 
drawn from Rastaben through Grumium, and produced about 14°, will point it out. A line 
drawn from Lyra through Zi Draconis, and produced 10° further, will point out Zeta, a 
star of the 3d magnitude, situated in the third coil. Zeta may otherwise be known, by its 
being nearly in a line with, and midway between, Etanin and Kochab. From Zeta, the 
remaining stars in this constellation are easily traced. 

Eta, Theta, and Asich, come next ; all stars of the 3d magnitude, and at the distance 
severally, of 6°, 4°, and 5° from Zeta. At Asich, the third star from Zeta, the tail of the 
Dragon makes a sudden crook. Thuban, Kappa, and Giansar, follow next, and com- 
plete the tail. 

212. Thuban is a bright star of the 2d magnitude, 11° from 
Asich, in a line with, and about midway between, Mizar and the 
southernmost guard in the Little Bear. By nautical men this 
star is called the Dragon's Tail, and is considered of much 
importance at sea. It is otherwise celebrated as being formerly 
the north polar star. About 2,300 years before the Christian 
Era, Thuban was ten times nearer the true pole of the heavens 
than Cynosura now is. 

Kappa is a star of the 3d magnitude, 10° from Alpha, between Megrez and the pole. 
Mizar and Megrez, in the tail of the Great Bear, form, with Thuban and Kappa, in the 
tail of the Dragon, a large quadrilateral figure, whose longest side is from Megrez to 
Kappa. 

Giansar, the last star in the tail, is between the 3d and 4th magnitudes, and 5° from 
Kappa. The two pointers will also point out Giansar, lying at the distance of little more 
than 8° from them, and in the direction of the pole. 

HISTORY. 

Mythologists give various accounts of this constellation. By some it is represented as 
the watchful dragon which guarded the golden apples in the famous garden of the Hes- 
perides, near Mount Atlas in Africa, and was slain by Hercules. Juno, who presented 
these apples to Jupiter on the day of their nuptials, took Draco up to heaven, and made a 
constellation of him, as a reward for his faithful services. Others maintain that in the war 
with the giants, this dragon was brought into combat, and opposed to Mineiva, who seized 
it in her hand, and hurled it, twisted as it was, into the heavens round the axis of the 
world, before it had time to unwind its contortions, where it sleeps to this day. Other 
writers of antiquity say, that this is the dragon killed by Cadmus, who was ordered by his 
father to go in quest of his sister Europa, whom Jupiter had carried away, and never to 
return to Phenicia without her. 

" When now Agenor had his daughter lost, 

He sent his son to search on every coast ; 

And sternly bade him to his arms restore 
* The darling maid, or see his face no more." 

214. Size and position of Thuban? What called by nautical men ? How otherwise 
celebrated? What further of Kappa, Mizar, Megrez, &c. ? 

History. — Various Mythological accounts? Story of Cadmus and the dragon's teeth ? 



112 ASTRONOMY. 

His search, however, proving fruitless, he consulted the oracle of Apollo, and was 
ordered to build a city where he should see a heifer stop in the grass, and to call the 
country Bceotia. He saw the heifer according to the oracle, and as he wished to render 
thanks to the god by a sacrifice, he sent his companions to fetch water from the neighbor- 
ing grove. The waters were sacred to Mars, and guarded by a most terrific dragon, who 
devoured all the messengers. Cadmus, tired of their seeming delay, went to the place, 
and saw the monster still feeding on their flesh. 

Cadmus, beholding such a scene, boldly resolved to avenge, or to share their fate. He 
therefore attacked the monster with slings and arrows, and, with the assistance of 
Minerva, slew him. He then plucked out his teeth, and sowed them, at the command of 
Pallas, in a plain, when they suddenly sprung up into armed men. 

Entertaining worse apprehension from the direful offspring than he had done from the 
dragon himself, he was about to fly, when they fell upon each other, and were all slain in 
one promiscuous carnage, except five, who assisted Cadmus to build the city of Bceotia. 

TELESCOPIC OBJECTS. 

1. a Draconis {Thubari) — A star with a distant companion in the fifth coil of Draco ; R. 
A. Uh. 00m. 08s. ; Dec. X. 65° OS' 04'. A 3j£, pale yellow; B 8, dusky ; two other stars in 
the field. Upwards of 4,600 years ago, this was the pole-star of the Chaldeans. 

2. 3 Draconis (Bastabtn) — A star with a very distant companion, in the eye of Draco ; 
R. A. 17h. 26m. 4Ss. ; Dec. X. 52° 25 02". A 2, yellow ; B 10, bluish ; other stars in field. 

8. y Draconis (Etaniii) — A star with a telescopic companion, in the crown of Draco; 
K. A. 17h. 52m. 58s. ; Dee. N. 51" 30' 06". A 2, orange tint ; B 12, pale lilac. A third star 
in the field making a neat triangle with A and B. Etanin is celebrated as the star by 
viewing which, Bradly discovered the aberration of light in 1725. It is a zenith-star at 
the Greenwich observatory. 

4. 6 Draconis — A bright star with a distant companion, in the second flexure ; R. A. 
19h. 12m. 30s. ; Dec. N. 67" 22' OS'. A 8, deep yellow ; B 9%, pale red; other small stars 
in the field. 

5. e Dracoxis — A fine double star between the second and third flexures ; R. A. 19h. 
4Sm. 41s. ; Dec. N. 69° 51' 6". A 5%, light yellow; B S, blue; a third star just north 
of a. 

6. i] Dracoxis — A star with a companion, between the third and fourth flexures ; R. A. 
16h. 21m. 4Ss. ; Dec. N. 61° 52' 04". A 3, deep yellow; B 11, pale grey. 

7. u Draconis — A verv neat binary system, on the tip of the Dragon's tongue ; R. A. 
17h. 02m. 02s. ; Dec. X. 54° 41 02". A 4. and B 43^, both white. Resembles Castor, 
though the components are nearer equal. Period, about 600 years. 

6. A triple star in the first flexure; R. A. ISh. 21m. 86s.; Dec. X. 5S° 42' 05". A 5, 
pale white; B SJg, light blue; C 7, ruddy. A difficult object — about midway between 
) and $. 

9. A beautiful triple star in the nose of Draco, on a line from y over ^, and near 
twice as much further ; R. A. 16h. 32m. 2Ss. ; Dec. X. 53° 14' 09". A 6, pale yellow; B 63$, 
faint lilac ; C 6, white ; four other stars in view. 

10. A bright-class, oval nebula, under the body of Draco ; R. A. 15h. 02m. 03s. ; Dec. 
X. 56° 23 0". Faint at the edges, with four stars in the field ; one quite near it. 

11. A planetary xebcla, between the second and third coil, on a line from Polaris to y 
Draconis: R. A. 17h. 5Sm. 3Ss. ; Dec. 66° 8S' 01". A remarkably bright and pale blue 
object, with several telescopic stars in the field. Map IX., Fig. 56. It is situated exactly 
i?i the pole of the ecliptic. 



LYRA (the harp).— MAP V. 

213. This constellation is distinguished by one of the most 
brilliant stars in the northern hemisphere. It is situated direct- 
ly south of the first coil of Draco, between the Swan on the 

Telescopic Objects.— Alpha ? Beta? Gamma? Delta? Epsilon? Eta? Mu? 
Triple stars ? Xebulas ? 

213. How is Lyra distinguished? Where situated? Xuniber and size of its princi- 
pal stars ? 



LYRA. 11$ 

east, and Hercules on the west ; and when on the meridian, is 
almost directly overhead. It contains twenty-one stars, includ- 
ing one of the 1st magnitude, two of the 3d, and as many of 
the 4th. 

There Lyra, for the brightness of her stars, 
More than their number, eminent ; thrice seven 
She counts, and one of these illuminates 
The heavens far around, blazing imperial 
In the first order." 

214. This star " blazing imperial in the first order" is called 
Vega, and sometimes Wega ; but more frequently, Lyra, after 
the name of the constellation. 

There is no possibility of mistaking this star for any other. 
It is situated 14f ° S. E. of Eltanin, and about 30° N. N. E. of 
Ras Alhague and Has Algethi. It may be certainly known by 
means of two small, yet conspicuous stars, of the 5th magnitude, 
situated about 2° apart, on the east of it, and making with it a 
beautiful little triangle, with the angular point at Lyra. 

The northernmost of these two small stars is marked Epsilon, and the southern one 
Zeta. About 2° S. E. of Zeta, and in a line with Lyra, is a star of the 4th magnitude, 
marked Delia, in the middle of the Harp ; and 4° or 5° S. of Delta, are two stars of the 
3d magnitude, about 2° apart, in the garland of the Harp, forming another triangle, whose 
vertex is in Delta. The star on the east is marked Gamma; that on the west, Beta. If 
a line be drawn from Etanin through Lyra, and produced 6° farther, it will reach Beta. 

This is a variable star, changing from the 3d to nearly the 5th magnitude in the space 
of a week ; it is supposed to have spots on its surface, and to turn on its axis, like 
our sun. 

Gamma comes to the meridian 21 minutes after Lyra, and precisely at the same 
moment with Epsilon, in the tail of the Eagle, 173<T S. of it. 

The remarkable brightness of a Lyra has attracted the admi- 
ration of astronomers in all ages. Manilius, who wrote in the 
age of Augustus, thus alludes to it : — 

'' One, placed in front above the rest, displays 
A vigorous light and darts surprising rays." 

Astronomicon, B. i. p. 15. 

HISTORY. 

It is generally asserted that this is the celestial Lyre which Apollo or Mercury gave to 
Orpheus, and upon which he played with such a masterly hand, that even the most rapid 
rivers ceased to flow, the wild beasts of the forest forgot then- wildness, and the moun- 
tains came to listen to his song. 

Of all the nymphs who used to listen to his song, Eurydyce was the only one who made 
a deep impression on the musician, and their nuptials were celebrated. Their happiDess, 
however, was short. Aristaeus became enamored of Eurydice, and as she fled from her 
pursuer, a serpent, lurking in the grass, bit her foot, and she died of the. wound. Orpheus 
resolved to recover her, or perish in the attempt. With his lyre in his hand, he entered 
the infernal regions, and gained admission to Pluto. The king of hell was charmed with 
his strains, the wheel of Ixion stopped, the stone of Sisyphus stood still, Tantalus forgot 
his thirst, and even the furies relented. 

Pluto and Proserpine were moved, and consented to restore him Eurydice, provided he 
forbore looking behind till he had come to the extremest borders of their dark dominions. 

214. Names of the most brilliant star ? How certainly known ? Where are Epsilon, 
Zeta, Delta, Gamma, and Beta? What peculiarity about Beta ? InaLyrae? 



114 ASTRONOMY. 

The condition was accepted, and Orpheus was already in sight of the upper regions of 
the air, when he forgot, and turned back to look at his long-lost Eurydice. He saw her, 
but she instantly vanished from his sight. He attempted again to follow her, but was 
refused admission. 

From this time, Orpheus separated himself from the society of mankind, which so 
offended the Thracian women, it is said, that they tore his body to pieces, and threw his 
head into the Hebrus, still articulating the words Eurydice I Eurydice ! as it was carried 
down the stream into the iEgean sea. Orpheus was one of the Argonauts, of which cele- 
brated expedition he wrote a poetical account, which is still extant. After his death, he 
received divine honors, and his lyre became one of the constellations. 

This fable, or allegory, designed merely to represent the power of music in the hands 
of the great master of the science, is similarly described by three of the most renowned' 
Latin poets. Virgil, in the fourth book of his Georgics, thus describes the effect of the 
lyre : — 

" E'en to the dark dominions of the night 

He took his way, through forests void of light, 

And dared amid the trembling ghosts to sing, 

And stood before the inexorable king. 

The infernal troops like passing shadows glide, 

And listening, crowd the sweet musician's side ; 

Men, matrons, children, and the unmarried maid, 

The mighty hero's more majestic shade, 

And youth, on funeral piles before their parents laid. 

E'en from the depths of hell the damn'd advance ; 

The infernal mansions, nodding, seem to dance ; 

The gaping three-mouth 'd dog forgets to snarl ; 

The furies hearken, and their snakes uncurl ; 

Ixion seems no more his pain to feel, 

But leans attentive on his standing wheel. 

All dangers past, at length the lovely bride 

In safety goes, with her melodious guide." 
Pythagoras and his followers represent Apollo playing upon a harp of seven strings, 
by which is meant (as appears from Pliny, b. ii. c. 22, Macrobius i. c. 19, and Censorius 
c. ii.), the sun in conjunction with the seven planets ; for they made him the leader of 
that septenary chorus, and the moderator of nature, and thought that by his attractive 
force he acted upon the planets in the harmonical ratio of their distances. 

The doctrine of celestial harmony, by which was meant the music of the spheres, was 
common to all the nations of the East. To this divine music Euripides beautifully 
alludes : — " Thee I invoke, thou self-created Being, who gave birth to Nature, and whom 
light and darkness, and the whole train of globes encircle with eternal music." — So also 
Shakspeare : — 

" Look, how the floor of heaven 

Is thick inlaid, with patines of bright gold ; 

There's not the smallest orb which thou behold'st, 

But in his motion like an angel sings, 

Still quiring to the young-eyed cherubim : 

Such harmony is in immortal souls ; 

But, while this muddy vesture of decay 

Doth grossly close it in, we cannot hear it." 

The lyre was a famous stringed instrument, much used among the ancients, said to 
have been invented by Mercury about the year of the world 2,000 ; though some ascribe 
the invention to Jubal. (Genesis iv. 21.) It is universally allowed, that the lyre was the 
first instrument of the string kind ever used in Greece. The different lyres, at various 
periods of time, had from four to eighteen strings each. The modern lyre is the Welsh 
harp. The lyre, among painters, is an attribute of Apollo and the Muses. 

All poetry, it has been conjectured, was in its origin lyric ; that is, adapted to recita- 
tion or song, with the accompaniment of music, and distinguished by the utmost boldness 
of thought and expression ; being at first employed in celebrating the praises of god3 
and heroes. 

Lesbos was the principal seat of the Lyric Muse ; and Terpander, a native of this 
island, who nourished about 650 years B. C., is one of the earliest of the Lyric poets 
whose name we find on record. Sappho, whose misfortunes have united with her talents 
to render her name memorable, was born at Mitylene, the chief city of Lesbos. She was 

History. — Story of Orpheus and Eurydice ? Design of this myth ? Celebrated by what 
poets ? Origin of the Lyre, and of Lyric poetry ? What said of Pindar ? 



TAURUS PONIATOWSKII. 115 

reckoned a tenth muse, and placed without controversy at the head of the female writers 
in Greece. But Pindar, a native of Thebes, who flourished about 500 years B. C, is 
styled the prince of lyric poets. To him his fellow-citizens erected a monument ; and 
when the Lacedemonians ravaged Bceotia, and burnt the capital, the following words 
were written upon the door of the poet: Forbear to burn this house. It was the 

DWELLING OF PlNDAR. 

TELESCOPIC OBJECTS. 

1. a Lyre — A star with a little companion ; R. A. 18h. 31m. 30s. ; Dec. N. 38° 38' 01". 
A 1, pale sapphire ; B 11, smalt blue. Map VIII., Pig. 15. 

a Lyria is computed to be 400,000 times as remote as our sun ; or 38,000,000,000,000 
distant ! And yet what is this to the mean distances of many of those of the 12th to 15th 
magnitudes ? 

2. j3 Lyr.e — A star with its companions forming a quadruple system; R. A. 18h. 44m. 
09s.; Dec. N. 33° 10' 08". A 3, very white and splendid; B 8, pale grey; C 8%, faint 
yellow ; D 9, light lilac. (3 is regarded as valuable. 

3. y Lyr,e — A lustrous star 7° southeast of Vega, with a minute distant companion '■> 
R. A. ISh. 52m. 57s. ; Dec. N. 32° 28' 05". A 3, bright yellow ; B 11, blue ; other tele- 
scopic stars in the field. 

4. e Lyr^e — A splendid multiple star, only 1}£° northeast of Vega ; R. A. 18h. 39m. 
02s. ; Dec. N. 39° 30' 03". Map VIII., Fig. 16. With small instruments it appears simply 
double ; but witli better instruments each of the components are found to be double, and 
binary systems. Between the twin systems are three minute stars. The components of 
the two systems are described as A 5, yellow; B 6%, ruddy; C 5, and D 5%, both white. 
A, B are the lowest, or northern pair. 

These two twin systems are in motion around a common center of gravity, as well as 
the respective components around each other. The period of the individual systems is 
estimated at about 2,000 years ; while 1,000,000 of years are supposed to be requisite for 
a revolution round the common center of both ! 

5. f Lyr^: — A fine double star about 2° south of £ ; R. A. 18h. 39m. 15s. ; Dec. N. 37* 
26' 05". A 5, topaz ;' B 53$, greenish. 

6. 7j Lyr.e — A neat double star 6° east of Vega; R. A. 19h. OSm. 18s. ; Dec. N. 3S° 52 
05". A 5, sky blue ; B 9, violet tint. A fine object for a moderate telescope. 

7. V LyRjE — A quadruple star in the cross-piece of the Lyre ; R. A. ISh. 43m. 48s. ; Dec. 
N. 32° 38' 0". A 9, pale yellow ; B 13, bluish ; C 11, pale blue ; D 15, blue ; three other 
stars in the field. A very delicate object. 

8. A globular cluster, in a splendid field, between the eastern yoke of Lyra and the 
head of Cygnus ; R. A. 19h. 10m. 19s, ; Dec. N. 29° 54' 02\ About 5%° southeast of Lyrse, 
towards /3 Cygni, and 3%° from the latter. Map IX., Fig. 57. 

9. An annular nebula between j3 and y, R. A. 18h. 47m. 37s.; Dec. N. 32* 50' 01". 
A wonderful object, in the form of an elliptical ring. Supposed by Herschel to be 900 
times as distant as Sirius. A clear opening through its center, and several stars in the 
field. Map IX., Fig. 58. 



TAURUS PONIATOWSKII.— MAP Y. 

215. This small asterism is between the shoulder of Ophiu- 
chus and the Eagle. The principal stars are in the head, and 
of the 4th magnitude. They are arranged in the form of the 
letter Y, and from a fancied resemblance to the zodiac Bull, and 
the Hyades, became another Taurus. See description of Ser- 
pentarius, article 206. 

Telescopic Objects. — Alpha? Beta? Gamma? Epsilon? Point out on the map. 
Zeta? Eta? Nu? What cluster? Point out on the map. What nebula, and where 
found on the map ? 

215. Describe Taurus Poniatowskii, Where situated ? 



116 ASTRONOMY. 

TELESCOPIC OBJECTS. 

1. A neat double star in the space between the Polish Bull, and the Eagle's wing, 8° 
east of a Ophiuchi, in a line towards Altair ; R. A. 17h. 5Sm. 17s. ; Dec. N. 11° 59' 08". 
A 8, straw-color; B8^, sapphire blue. 

2. A fine planetary nebula, in a rich vicinity, in the shoulder; R. A. 18h. 04m. 21s. ; 
Dec. N. 6° 49' 02". A small but bright object, regarded by Prof. Struve as one of the most 
curious in the heavens. Many telescopic stars in the field. 



SCUTUM SOBIESKI (sobieski's shield).— MAP Y. 

216. This small figure is between the head of the Polish Bull, 
and the head of Sagittarius. Its four principal stars are of the 
5th magnitude ; and it is important chiefly for its Telescopic 
Objects. 

TELESCOPIC OBJECTS. 

1. A double star 1%' northeast of jit Sagittarii ; R. A. 18h. 07m. 37s.; Dec. S. 19" 55' 
05". A 8 %, and B 10, both grey. 

2. A nea* double star, in a long and straggling assemblage below the Shield ; R. A. 
ISh. 10m. 36s. ; Dec. S. 17° 11' 07". A 9, and B 11. both bluish. It is 4° from [i Sagittarii, 
in a very rich vicinity; several splendid fields lying only about 1° south of it. 

3. A beautiful cluster below the base of the Shield ; R. A. 18h. 08m. 49s. ; Dec. S. 18* 
27' 05". A line from a Aquilae, southwest over 2. Antinoi, and continued as far again, 
will reach this object. 

4. A scattered but large cluster, north-half-east from fi Sagittarii 7° ; R. A. 18h. 
09ra. 44s. ; Dec. S. 13° 50' 05". Stars disposed in pairs, the whole forming a very pretty 
object in a telescope of tolerable capacity. 

5. A horse-shoe nebula just below the Shield ; R. A. 18h. 1 lm. 23s. ; Dec. S. 16° 15' 08". 
It has been compared to a Greek £2. Map IX., Fig. 59. Five stars in the object, and 
others in the field, and the region around it particularly rich. Sir William Herschel 
computed that there were 285,000 stars in a space 10° long, and 2%° wide; many of 
which were 2,300 times as far off as Sirius ! 



SAGITTAKIUS (the archer).— MAP Y. 

217. This is the ninth sign and the tenth constellation of the 
Zodiac. It is situated next east of Scorpio, with a mean decli- 
nation of 35° S., or 12° below the ecliptic. The sun enters this 
sign on the 22d of November, but does not reach the constel- 
lation before the 1th of December. It occupies a considerable 
space in the southern hemisphere, and contains a number of sub- 
ordinate, though very conspicuous stars. The whole number of 
its visible stars is sixty-nine, including five of the 3d magnitude, 
and ten of the 4th. 



Telescopic Objects. — What double star ? What nebula ? 

216. Situation and components of Scotum Sobieski? For what chiefly important t 
Telescopic Objects. — What double stars? Clusters? Nebula? 

217. Order of Sagittarius, in the signs and constellations? When does the sun enter 
this sign t The constellation ? Its extent ? Number and size of its stars ? 



SAGITTARIUS. 117 

218. Sagittarius may be readily distinguished by means of five 
stars of the 3d and 4th magnitudes, forming a figure resem- 
bling a little, short, straight-handled dipper, turned nearly bot- 
tom upward, with the handle to the west, familiarly called the 
Milk-Dipper, because it is partly in the Milky-Way. 

This little figure is so conspicuous that it cannot easily be 
mistaken. It is situated about 33° E. of Antares, and comes 
to the meridian a few minutes after Lyra, on the ltth of Au- 
gust. Of the four stars forming the bowl of the Dipper, the two 
upper ones are only 3° apart, and the lower ones 5°. 

The two smaller stars forming the handle, and extending westerly about 4%°, and the 
easternmost one in the bowl of the Dipper, are all of the 4th magnitude. The star in 
the end of the handle, is marked Lambda, and is placed in the bow of Sagittarius, just 
within the Milky- Way. Lambda may otherwise be known by its being nearly in a line 
with two other stars about 4%° apart, extending toward the S. E. It is also equidistant 
from Phi and Delta, with which it makes a handsome triangle, with the vertex in 
Lambda. About 5° above Lambda, and a little to the west, are two stars close together 
in the end of the bow, the brightest of which is of the 4th magnitude, and marked Mu. 
This star serves to point out the winter solstice, being about 2° N. of the tropic of Capri- 
corn, and less than one degree east of the solstitial colure. 

If a line be drawn from Sigma through Phi, and produced about 6° farther to the west, 
it will point out Delta, and produced about 3° from Delta, it will point out Gamma; stars 
of the 3d magnitude, in the arrow. The latter is in the point of the arrow, and may be 
known by means of a small star just above it, on the right. This star is so nearly on the 
same meridian with Etanin, in the head of Draco, that it culminates only two minutes 
after it. 

A few other conspicuous stars in this constellation, forming a variety of geometrical 
figures, may be easily traced from the map. 

HISTORY. 

This constellation, it is said, commemorates the famous Centaur Chiron, son of Philyra 
and Saturn, who changed himself into a horse, to elude the jealous inquiries of his wife 
Rhea. 

Chiron was famous for his knowledge of music, medicine and shooting. He taught 
mankind the use of plants and medicinal herbs; and instructed, in all the polite arts, 
the greatest heroes of the age. He taught iEsculapius physic, Apollo music, and Her- 
cules astronomy; and was tutor to Achilles, Jason, and iEneas. According to Ovid, he 
was slain by Hercules, at the river Evenus, for offering indignity to his newly married 
bride. 

" Thou monster double shap'd, my right set free — 
Swift as his words, the fatal arrow flew ; 
The Centaur's back admits the feather'd wood, 
And through his breast the barbed weapon stood ; 
Which, when in anguish, through the flesh he tore, 
From both the wounds gush'd forth the spumy gore." 
The arrow which Hercules thus sped at the Centaur, having been dipped in the blood 
of the Lernsean Hydra, rendered the wound incurable, even by the father of medicine 
himself, and he begged Jupiter to deprive him of immortality, if thus he might escape 
his excruciating pains. Jupiter granted his request, and translated him to a place 
among the constellations. 

" Midst golden stars he stands refulgent now, 
And thrusts the Scorpion with his bended bow." 
This is the Grecian account of Sagittarius ; but as this constellation appears on the 
ancient zodiacs of Egypt, Dendera, Esne, and India, it seems conclusive that the Greeks 

218. How distinguished? Where is Lambda? How known? , Where are Mu, Delta, 
and Gamma ? 

History. — What does Sagittarius commemorate? Story of Chiron? What said of the 
antiquity of this constellation? 



118 ASTRONOMY. 

only borrowed the, figure, while they invented the fable. This is known to be true with 
respect to very many of the ancient constellations. Hence the jargon of the conflicting 
accounts which have descended to us. 

TELESCOPIC OBJECTS. 

1. jU SAGiTTARn — A multiple star in the north end of the Archer's bow; R. A. 18h. 
04m. lis. ; Dec. S. 21° 05' 07" About 25° east-northeast of Antares. A ?>%, pale yellow ; 
B 16, blue ; C 9H, and D 10, both reddish. 

2. er Sagittarii — A star with a distant companion in the Archer's right shoulder; 
R. A. ISh. 45m. 20s. ; Dec. S. 26° 29' 03". A 3, ruddy ; B 9%, ash-colored. 

3. A very delicate triple star, between the heads of Sagittarius and Capricorn, about 
25° south-by-west of Altair, and 10° west of & Capricorni ; R. A. 19h. 31m. 33s. ; Dec. S. 
16° 39' 02". A 5%, yellow ; B 8, violet ; C 16, blue. Other small stars in the field. 

4. A large and coarse cluster of minute stars, close to the upper end of the bow, and 
In the Galaxy; R. A. 18h. 03m. 08s. ; Dec. S. 21° 36' 01". Stars of the 10th to 13th mag- 
nitudes. A rich field of no particular form. 

5. A loose cluster in the Galaxy, between the Archer's head and Sobieski's Shield ; 
R. A. 18h. 22m. 14s. ; Dec. S. 19° 10' 02". The most prominent are a pair of 8th magni- 
tude stars. It is about 5° northeast of ^ Sagittarii. 

6. A fine globular cluster between the head and bow, near the solsticial colure ; 
R. A. 18h. 26m. 25s. ; Dec. S. 24° 01' 04". A fine group, compressed towards the center, 
with several single stars in the field. Map IX., Fig. 60. 



CORONA AUSTRALIS (the southern crown).— MAP V. 

219. This is a small and unimportant constellation near the 
fore-legs of Sagittarius ; and between them and the Milky-Way. 
R. A. about 18h. 44m.; Dec. S. 40°. Its four principal stars 
are of the 5th magnitude, situated near each other, and arranged 
in a gentle curve line, lying north and south. It has no Mytho- 
logical History, or Telescopic Objects worthy of notice. 



AQUILA ET ANTTOOUS (the eagle and antinotjs).— MAP V. 

220. This double constellation is situated directly south of 
the Fox and Goose, and between Taurus Poniatowskii on the 
west, and the Dolphin on the east. It contains seventy-one 
stars, including one of the 1st magnitude, nine of the 3d, and 
seven of the 4th. It may be readily distinguished by the 
position and superior brilliancy of its principal star. 

221. Altair, the principal star in the Eagle, is of the 1st, or 
between the 1st and 2d magnitudes. It is situated about 14° 

Telescopic Objects.— Mu? Sigma? What triple star? What clusters? Which 
shown on the map ? Point it out. 
219. Describe Corona Australis. Its principal stars ? History and Telescopic Objects ? 

220. Situation of Aquila and Antinous? Number and size of its principal stars? 

221. Altair — how known? Stars each side of it? Use of Altair in navigation? What 



AQUILA ET ANTINOUS. 119 

S. W. of the Dolphin. It may be known by its being the 
largest and middle one of the three bright stars which are 
arranged in a line bearing N. W. and S. E. The stars on each 
side of Altair are of the 3d magnitude, and distant from it about 
2°. This row of stars very much resembles that in the Guards 
of the Lesser Bear. 

Altair is one of the stars from which the moon's distance is 
taken for computing longitude at sea. Its mean declination is 
nearly 8£° N., and when on the meridian, it occupies nearly the 
same place in the heavens that the sun does at noon on the 12th 
day of April. It culminates about 6 minutes before 9 o'clock, 
on the last day of August. It rises acronically about the begin- 
ning of June. 

Ovid alludes to the rising of this constellation ; or, more probably, to that of the prin- 
cipal star, Altair : — 

" Now view the skies, 

And you'll behold Jove's hook'd-bill bird arise." 

Massey's Fasti. 



Among thy splendid group 



One dubious whether of the Second rank, 
Or to the First entitled ; but whose claim 
Seems to deserve the First." 

Eudosia. 

The northernmost star in the line, next above Altair, is called Tarazed. In the wing 
of the Eagle, there is another row composed of three stars, situated 4° or 5° apart, 
extending down toward the southwest; the middle one in this line is the smallest, being 
only of the fourth magnitude ; the next is of the 3d magnitude, marked Delta, and 
situated 8° S. W. of Altair. 

As you proceed from Delta, there is another line of three stars of the 3d magnitude, 
between 5° and 6° apart, extending southerly, but curving a little to the west, which 
mark the youth Antinous. The northern wing of the Eagle is not distinguished by any 
conspicuous stars. 

Zeta and Epsilon, of the 3d magnitude, situated in the tail of the Eagle, are about 2° 
apart, and 12° N. W. of Altair. The last one in the tail, marked Epsilon, is on the same 
meridian, and culminates the same moment with Gamma, in the Harp. 

From Epsilon, in the tail of the Eagle, to Theta, in the wrist of Antinous, may be traced 
a long line of stars, chiefly of the 3d magnitude, whose letter names are Theta, Eta, Mu, 
Zeta and Epsilon. The direction of this line is from S. E. to N. W., and its length is 
about 25°. 

Eta is remarkable for its changeable appearance. Its greatest brightness continues 
but 40 hours ; it then gradually diminishes for 66 hours, when its luster remains station- 
ary for 30 hours. It then waxes brighter and brighter, until it appears again as a star 
of the 3d magnitude. 

From these phenomena, it is inferred that it not only has spots on its surface, like our 
sun, but that it also turns on its axis. 

Similar phenomena are observable in Algol, Beta, in the Hare, Delta, in Cepheus, and 
Omicron, in the Whale, and many others. 

1 Aquila the next, 



Divides the ether with her ardent wing : 
Beneath the Swan nor far from Pegasus, 
Poetic Eagle." 



poetic quotation ? Where are Tarazed and Delta ? Zeta and Epsilon ? Theta ? Eta ? 
For what remarkable ? 



120 ASTRONOMY. 



HISTORY. 

Aquila, or the Eagle, is a constellation usually joined with Antinous. Aquila is sup- 
posed to have been Merops, a king of the island of Cos, in the Archipelago, and the hus- 
band of Clymene, the mother of Phaston ; this monarch having been transformed into an 
eagle, and placed among the constellations. Some have imagined that Aquila was the 
eagle whose form Jupiter assumed when he carried away Ganymede ; others, that it 
represents the eagle which brought nectar to Jupiter while he lay concealed in the cave at 
Crete, to avoid the fury of his father, Saturn. Some of the ancient poets say, that this 
is the eagle which furnished Jupiter with weapons in his war with the giants : — 
" The towering Eagle next doth boldly soar, 
As if the thunder in his claws he bore ; 
He's worthy Jove, since he, a bird, supplies 
The heaven with sacred bolts, and arms the skies." 

MaiiiUus. 
The eagle is justly styled the "sovereign of birds," since he is the largest, strongest, 
and swiftest of all the feathered tribe that live by prey. Homer calls the eagle, " the 
strong sovereign of the plumy race ;" Horace styles him — 

" The royal bird, to whom the king of heaven 
The empire of the feathered race has given :" 

And Milton denominates the eagle the " Bird of Jove." Its sight is quick, strong and 
piercing, to a proverb : Job xxix., 28, &c. 

" Though strong the hawk, though practised well to fly, 
An eagle drops her in the lower sky ; 
An eagle when deserting human sight. 
She seeks the sun in her unwearied flight ; 
Did thy command her yellow pinion lift 
So high in air, and set her on the clift 
Where far above thy world she dwells alone, 
And proudly makes the strength of rocks her own ; 
Thence wide o'er nature takes her dread survey, 
And with a glance predestinates her prey? 
She feasts her young with blood; and hovering o'er 
The unslaughtered host, enjoys the promised gore." 

ANTINOUS. 

Antinous is a part of the constellation Aquili, and was invented by Tycho Brahe 
Antinous was a youth of Bithynia, in Asia Minor. So greatly was his death lamented 
by the emperor Adrian, that he erected a temple to his memory, and built in honor of 
him a splendid city, on the banks of the Nile, the ruins of which are still visited by 
travelers with much interest. 

TELESCOPIC OBJECTS. 

1. a Aquila (AUair) — A bright star in the neck, with a distant companion ; R. A. 
19h. 42m. 58s. ; Dec. N. 8° 26' 09". A 1%, pale yellow; B 10, violet tint. 

2. /3 Aquila (Alskain) — A double star, also in the neck of Aquila, and the head of 
Antinous; R. A. 19h. 4Tm. 26s.; Dec. N. 6° 00' 07". About 2%° south-southeast of 
Altair. A 3%, pale orange ; B 10, pale grey ; with other stars in the field. 

3. y Aquila {Tarazed)—K star in the back of Aquila, on a line with a and /3, with a 
minute companion ; R. A. 19h. 38m. 38s. ; Dec. N. 10° 13' 06". A 3, pale orange; B 12, 
dusky; other stars around. 

4. 6 Aquilje, in the southern wing ; R. A. 19h. 17m. 25s. ; Dec. N. 2° 48' 00". Has a 
distant companion. A 3%, white ; B 12, livid; other stars in the field. 

5. £ Aquilje, in the tail; R. A. 18h. 58m. 02s. ; Dec. N. 13° 37' 08". A 3, greenish tint ; 
B 11, livid ; two other stars in the field. 

6. A neat double star on the margin of the lower wing; R. A. 18h. 57m. 59s. ; Dec. N. 
6° 18' 08". A 7J£, lucid white ; B 9, cerulean blue. A fine object, not difficult to find, as 

History. — Different suppositions respecting? Manilius? Horace? Milton? What 
said of Antinous? 

Telescopic Objects. — Alpha? Beta? Gamma? Delta? Xi? Other double stars? 
What clusters ? Which shown on the map ? What nebula ? 



SAGITTA ANSER ET VULPECULA. 121 

it lies 10° due north of X Antinoi, a 8d magnitude star, and 13° west of $ Aquilse. The 
brightest object of its immediate neighborhood. 

7. A wide double star about 4° west-by-south of a Antinoi, between the foot and 
Sobieski's Shield ; R. A. ISh. 41m. 07s. ; Dec. S. 6° 05' 03°. A 7, orange tint; B 9, ceru- 
lean blue. Many telescopic stars in the field. 

8. A splendid cluster close to the southeast of the last described object; R. A. 18h. 
12m. 32s. ; Dec. S. 6° 27' 02". It is between the left foot and Sobieski's Shield. A gor- 
geous object " somewhat resembling a flight of wild ducks in shape," has an 8th magni- 
tude star in the middle, and two larger east of it ; probably all three between us and 
the cluster. Map IX., Fig. 61. 

9. A loose cluster between the lower wing and the leg of Antinous, and 13° southwest 
of Altair, on a line from Tega through e Aquilse ; R. A. 19h. 08m. 36s. ; Dec. S. 1° 11' 09" 
A splashy group of stars from the 9th to the 12th magnitudes, on the eastern margin of 
the Galaxy. 

10. A stellar nebula on the Eagle's back, about 5° west of Altair; R. A. 19h. 23m. 
55s. ; Dec. N. 8° 54' 01". A minute object in the Milky- Way ; and in the most powerful 
telescopes, fan-shaped. 



SAGITTA (the aeeow.)— MAP Y. 

222. Sagitta is a small but old constellation between the 
Fox and Goose on the north, and the Eagle on the south. Its 
two principal stars are of the 4th magnitude, and lie nearly east 
and west, about 4° apart. The next two largest stars are of the 
5th magnitude. 

TELESCOPIC OBJECTS. 

1. £ Sagitta:— A star with a distant companion about 8° north-northwest of Altair, on 
a line towards Yega; R. A. 19h. 30m. 03s. ; Dec. N. 16° 06' 5". A 6, pale white ; B 8, 
light blue. 

2. f Sagitta — A neat double star just above the Arrow, 9° south by east from 3 
Cygni, and 10° north of Altair; R. A. 19h. 41m. 53s.; Dec N. 18° 44' 8". A 5, silvery 
white ; B 9, blue. 

3. $ Sagitta — A triple star near the head of the Arrow, about half-wav from \3 
Cygni to a Delphini; R. A. 20h. 02m. 53s. ; Dec. N. 20° 26' 6". A 7, pale topaz ; B 9, grey ; 
C S, pearly yellow. 

4. A rich compressed cluster on the shaft of the arrow, 10° northeast of Altair ; 
R. A. 19h. 46m. 36s. ; Dec. N. IS" 22' 1". Telescopic stars around it. 



AN"SER ET VULPECULA (the fox axd goose).— MAP Y. 

223. This is a modern constellation, situated between the 
Swan on the north, and the Arrow or the Dolphin and Eagle on 
the south. It is composed of some thirty stars, the largest of 
which is of the 3d magnitude. 

TELESCOPIC OBJECTS. 
1. A star with a distant companion on the nose of Reynard, and neck of the Goose, 
8%° south of (3 Cygni ; R. A. 19h. 22m. 03s. ; Dec. N. 24° 20' 7". 



222. Describe Sagitta — its principal stars. 

Telescopic Objects. — Epsilon? Zeta? What triple star? Cluster? 

223. Describe the Fox and Goose. Its component stars ? 



122 ASTRONOMY. 

2. A wide double Star, 11J6 north of Altair, between the Fox and the Arrow, in the 
eastern edge of the Galaxy; R. A. 19h. 46m. 20s.; Dec. N. 19° 55' 5". A and B both 7 
and both white. 

3. A large straggling cluster on the neck of the Goose, and about 3° from (3 Cygni; R. A 
I9h. 20m. 30s. ; Dec. N. 24° 49' 3". Two 7th magnitude stars in the west. The cluster 
has the form of a Greek £2. 

4. The celebrated dumb-bell nebula, on the Fox's breast, about 7° southeast of Cygni, 
and nearly half-way between it and the Dolphin; R. A. 19h. 52m. 89s. ; Dec. N. 22° 17' 1". 
(Map IX., Fig. 62.) This magnificent and singular object is in a crowded vicinity, where 
field after field is very rich. 



CHAPTER XI. 

CONSTELLATIONS ON THE MERIDIAN IN SEPTEMBER, 

DELPHINUS (the dolphin).— MAP Y. 

224. This beautiful little cluster of stars is situated 13° or 
J 4° N. E. of the Eagle. It consists of eighteen stars, including 
four of the 3d magnitude, but none larger. It is easily distin- 
guished from all others, by means of the four principal stars in 
the head, which are so arranged as to form the figure of a dia- 
mond, pointing N. E. and S. W. To many, this cluster is 
known by the name of JoVs Coffin ; but from whom, or from 
what fancy, it first obtained this appellation, is not known. 

225. There is another star of the 3d magnitude, situated in 
the body of the Dolphin, about 3° S. W. of the Diamond, and 
marked Epsilon. The other four are marked Alpha, Beta, 
Gamma, Delta. Between these are several smaller stars, too 
small to be seen in presence of the moon. 

The mean declination of the Dolphin is about 15° N". It 
comes to the meridian the same moment with Deneb Cygni, and 
about 50 minutes after Altair, on the 16th of September. 

s " Thee I behold, majestic Cyqnus, 

On the marge dancing of the heavenly sea, 
Arion's friend ; eighteen thy stars appear — 
One telescopic." 



Telescopic Objects. — What double stars? Cluster? Nebula ? Point out on the map. 

224. Constellations in this chapter? Delphinus? Number and size of stars? How 
distinguished? What other name has this constellation? 225. Where are Epsilon, 
Alpha, Beta, Gamma and Delta ? Mean declination, &c. 



DELPHINUS. 123 



HISTORY. 

The Dolphin, according to some raythologists, was made a constellation by Neptune 
because one of these beautiful fishes had persuaded the goddess Aniphitrite, who had made 
a vow of perpetual celibacy, to become the wife of that deity; but others maintain, that 
it is the dolphin which preserved the famous lyric poet and musician Arion, who was a 
native of Lesbos, an island in the Archipelago. 

He went to Italy with Periander, tyrant of Corinth, where he obtained immense riches 
by his profession. Wishing fo revisit his native country, the sailors of the ship in which 
he embarked resolved to murder him, and get possession of his wealth. Seeing them 
immovable in their resolution, Arion begged permission to play a tune upon his lute 
before he should be put to death. The melody of the instrument attracted a number of 
dolphins around the ship ; he immediately precipitated himself into the sea ; when one 
of them, it is asserted, carried him safe on his back to Tcenarus, a promontory of Laco- 
nia, in Peloponnesus ; when he hastened to the court of Periander, who ordered all the 
sailors to be crucified at their return. 

" But (past belief), a dolphin's arched back 
Preserved Arion from his destined wrack ; 
Secure he sits, and with harmonious strains 
Requites his bearer for his friendly pains." 

When the famous poet Hesiod was murdered in Naupactum, a city of iEtolia, in Greece, 
and his body thrown into the sea, some dolphins, it is said, brought back the floating 
corpse to the shore, which was immediately recognized by his friends ; and the assassins 
being afterwards discovered by the dogs of the departed bard, were put to death by 
immersion in the same sea. 

Taras, said by some to have been the founder of Tarentum, now Tarento, in the south 
of Italy, was saved from shipwreck by a dolphin ; and the inhabitants of that city pre- 
served the memory of this extraordinary event on their coin. 

The natural shape of the dolphin, however, is not incurvated, so that one might ride 
upon its back, as the poets imagined, but almost straight. When it is first taken from 
the water, it exhibits a variety of exquisitely beautiful but evanescent tints of color, that 
pass in succession over its body until it dies. They are an extremely swift-swimming 
fish, and are capable of living a long time out of water; in fact, they seem to delight to 
gambol, and leap out of their native element. 

" Upon the swelling waves the dolphins show 
Their bending backs ; then swiftly darting go, 
And in a thousand wreaths their bodies show." 

TELESCOPIC OBJECTS. 

1. a Delphini — A bright star with a distant telescopic companion ; R. A. 20h. 32m. 
12s. ; Dec. N. 15° 21' 01". A 3%, pale white ; B 13, blue. 

2. j3 Delphtm — A delicate triple star on the Dolphin's body, 1%° south-by-west of a, 
in a line with j3 Cygni and y Lyras; R. A. 20h. 30m. 03s.; Dec. N. 14' 02' 06". A 4, 
greenish tinge ; B 15, and C 12, both disky. 

3. y Delphini — A beautiful double star in the head, 2° east of a ; R. A. 20h. 39m. 
15s.; Dec. N. 15° 33' 02". A 4, yellow; B 7, light emerald, with a third star about 2" 
distant. 

4. A delicate quadruple star, near e in the tail ; R. A. 20h. 23m. 35s. ; Dec. N. 10° 43' 
06". A 7J3, and B 8, both white ; C 16, blue ; D 9, yellowish ; several other small stars 
in the field. Map VIIL, Fig. 17. 

5. A small bright cluster, in the Dolphin's tail, 3%° south of e ; R. A. 20h. 26m. 21s. ; 
Dec. N. 6° 53' 02". Just east of a 9th magnitude star — a coarse telescopic pair at a 
distance, and several minute stars in the field. 

6. A small planetary nebula, betwen the pectoral fin and the arrow head, 6° north- 
northwest of a, and exactly on a line towards Vega Lyras ; R. A. 20h. 15m. 15s. ; Dec. N. 
19° 35, 06". It is in a coarse cluster, in the center of which are four conspicuous stars. 

History. — Accounts of the origin of Delphinus? What said of Hesiod? Of Taras? 
Of the natural shape, &c? 

Telescopic Objects. — Alpha? Beta? Gamma? What quadruple star? Point out 
on the map. What cluster? Nebula? 



B.G. 6 



124 ASTRONOMY. 



CYGNUS (the swan).— MAP T. 

226. This remarkable constellation is situated in the Milky- 
Way, directly E. of Lyra, and nearly on the same meridian with 
the Dolphin. It is represented on outspread wings, flying down 
the Milky-Way, toward the southwest. 

The principal stars which mark the wings, the body and the 
bill of Cygnus, are so arranged as to form a large and regular 
Cross ; the upright piece lying along the Milky-Way from N. E. 
to S. W., while the cross piece, representing the wings, crosses 
the other at right angles, from S. E. to N. W. 

227. Arided or Dene.b Cygni, in the body of the Swan, is a 
star of the second magnitude, 24° E. N. E. of Lyra, and 30° 
directly N. of the Dolphin. It is the most brilliant star in the 
constellation. It is situated at the upper end of the cross, and 
comes to the meridian at 9 o'clock on the 16th of September. 

Sad'r is a star of the 3d magnitude, 6° S. W. of Deneb, situated exactly in the cross, 
or where the upright piece intersects the cross piece, and is about 20° E. of Lyra. 

Delta, the principal star in the west wing, or arm of the cross, is situated N. W. of 
Sad'r, at the distance of little more than 8°, and is of the 3d magnitude. Beyond Delta, 
toward the extremity of the wing, are two smaller stars about 5° apart, and inclining a 
little obliquely to the north ; the last of which reaches nearly to the first coil of Draco. 
These stars mark the west wing; the east wing may be traced by means of stars very 
similarly situated. 

Gienah is a star of the 3d magnitude, in the east wing, just as far east of Sad'r in the 
center of the cross, as Delta is west of it. This row of three equal stars, Delta, Sad'r 
and Gienah, form the bar of the cross, and are equi-distant from each other, being about 
8° apart. Beyond Gienah on the east, at the distance of 6° or 7°, there are two other 
stars of the 3d magnitude; the last of which marks the extremity of the eastern wing. 

The stars in the neck are all too small to be noticed. There is one, however, in the 
beak of the Swan, at the foot of the cross, called Albireo, which is of the 3d magnitude, 
and can be seen very plainly. It is about 16° S. W. of Sad'r, and about the same dis / - 
tance S. E. of Lyra, with which it makes nearly a right angle. 

" In the small space between Sad'r and Albireo," says Dr. Herschel, " the stars in the 
Milky- Way seem to be clustering into two separate divisions ; each division containing 
more than one hundred and sixty-five thousand stars." 

Albireo bears northerly from Altair, about 20*. Immediately south and southeast of 
Albireo, may be seen the Fox and Goose ; and about midway between Albireo and Altair, 
there may be traced a line of four or five minute stars, called the Arrow ; the head of 
which is on the S. W., and can be distinguished by means of two stars situated close 
together. 

228. According to the British catalogue, this constellation 
contains eighty-one stars, including one of the 1st or 2d magni- 
tude, six of the 3d, and twelve of the 4th. The author of the 
following beautiful lines says there are one hundred and seven. 

" Thee, silver Swan, who, silent, can o'erpass? 
A hundred with seven radiant stars compose 
• Thy graceful form : amid the lucid stream 

226. Situation of Cygnus? How represented? Figure made by its principal stars? 
Its position? 227. Which is the brightest of its stars? Describe Sad'r, Delta, Gienah, 
Albireo. Remark of Dr. Herschel? 228; Number of stars in Cygnus? Variable 
stars ? What are they supposed to indicate ? 



CYGNUS. 125 

Of the fair Milky- Way distinguished : one 

Adorns the second order, where she cuts 

The waves that follow in her utmost track ; 

This never hides its fire throughout the night, 

And of the rest, the more conspicuous mark 

Her snowy pinions and refulgent neck." — JEudosia, b. iv. 

Astronomers have discovered three variable stars in the Swan. Chi, situated in the 
neck, between Beta and Sad'r, was first observed to vary its brightness in 1686. Its peri- 
odical changes of light are now ascertained to be completed in 405 days. Sad'r is also 
changeable. Its greatest luster is somewhat less than that of a star of the 3d magnitude, 
and it gradually diminishes till it reaches that of the 6th. Its changes are far from being 
regular, and, from present observations, they do not seem to recur till after a period of 
ten years or more. 

A third variable star was discovered in the head on the 20th of June, 1670, by Anthelme. 
It appeared then to be of the 3d magnitude, but was so far diminished in the following 
October, as to be scarcely visible. In the beginning of April, 1671, it was again seen, and 
was rather brighter than at first. After several changes, it disappeared in March, 1672, 
and has not been observed since. 

These remarkable facts seem to indicate, that there is a brilliant planetary system in 
this constellation, which, in some of its revolutions, becomes visible to us. 

HISTORY. 

Mythologists give various accounts of the origin of this constellation. Some suppose 
it is Orpheus, the celebrated musician, who, on being murdered by the cruel priestess of 
Bacchus, was changed into a Swan, and placed near his Hai-p in the heavens. Others 
suppose it is the swan into which Jupiter transformed himself when he deceived Leda, 
wife of Tyndarus, king of Sparta. Some affirm that it was Cycnus, a son of Neptune, 
who was so completely invulnerable that neither the javelins nor arrows, nor even the 
blows of Achilles, in furious combat, could make any impression. 

" Headlong he leaps from off his lofty car, 
■ And in close fight on foot renews the war ; — 

But on his flesh nor wound nor blood is seen, 

The sword itself is blunted on the skin." 

But when Achilles saw that his darts and blows had no effect on him, he immediately 
threw him on the ground and smothered him. While he was attempting to despoil him 
of his armor, he was suddenly changed into a swan. 

"With eager haste he went to strip the dead; 
The vanished body froin his arms was fled. 
His sea-god sire, to immortalize his fame, 
Had turned it to a bird that bears his name." 

According to Ovid, this constellation took its name from Cycnus, a relative of Phaeton, 
who deeply lamented the untimely fate of that youth, and the melancholy end of his 
Bisters, who, standing around his tomb, wept themselves into poplars. 

" Cycnus beheld the nymphs transformed, allied 
To their dead brother on the mortal side, 
In friendship and affection nearer bound ; 
He left the cities, and the realms he owned, 
Through pathless fields, and lonely shores to range ; 
And woods made thicker by the sisters' change : 
While here, within the dismal gloom alone, 
The melancholy monarch made his moan ; 
His voice was lessened as he tried to speak, 
And issued through a long-extended neck: 
His hair transforms to down, his fingers meet 
In skinny films, and. shape his oary feet ; 
From both his sides the wings and feathers break ; 
And from his mouth proceeds a blunted beak ; 
AH Cycnus now into a swan was turned." — Ovid's Met. b. ii. 

History. — Various accounts ? Story of Cycnus and Achilles ? Ovid's account? Vir- 
gil's remarks respecting the Swan ? 



126 ASTRONOMY. 

Virgil, also, in the 10th book of his iEneid, alludes to the same fable : — 
M For Cycnus loved unhappy Phaeton, 
And sung his loss in poplar groves alone 
Beneath the sister shades to soothe his grief; 
Heaven heard his song, and hasten'd his relief 
And changed to snowy plumes his hoary hair, 
And wing'd his flight to sing aloft in air." 

Of all the feathered race, there is no bird, perhaps, which makes so beautiful and 
majestic an appearance as the, swan. Almost every poet of eminence has taken notice 
of it. The swan has, probably, in all ages, and in every country where taste and ele- 
gance have been cultivated, been considered as the emblem of poetical dignity, purity, 
and ease. By the ancients it was consecrated to Apollo and the Muses ; they also enter- 
tained a notion that this bird foretold its own end, and sang more sweetly at the 
approach of death. 

" She, like the swan 

Expiring, dies in melody." — ^Eschylus. 
" So on the silver stream, when death is nigh, 
The mournful swan sings its own elegy." — Ovid's Tristia. 

TELESCOPIC OBJECTS. 

1. a Ctgni (Deneb) — A bright star on the back of the Swan, with a telescopic com- 
panion ; R. A. 20h. 35m. 57s. ; Dec. N. 44° 42' 07". A 1, brilliant white ; B 12)3, pale blue. 

2. /? Cygni (AlMreo)—A bright double star on the bill of the figure ; R. A. 19h. 24ra. 
16s. ; Dec. N. 27° 37' 07". About 13 V south-southeast of Vega. A 3, topaz yellow ; B 7, 
sapphire blue ; the colors in brilliant contrast. A fine object, and the first double star 
ever seen by the present editor. 

3. d Cygni — A most delicate double star in the middle of the left wing, 14° west of a 
Cygni; R. A. 19h. 39m. 58s.; Dec. N. 44° 44' 06". A 3%, pale yellow; B 9, sea green. 
Another beautiful object. 

4. (, Cygni — A star with a distant companion, on the tip of the right wing ; R. A. 21h. 
06m. 07s.; Dec. N. 29° 34' 05". A 8, pale yellow; B 10, sky blue; the field rich in 
small stars. 

5. "k Cygni — A close double star in the right or lower wing, with a distant companion ; 
R. A. 20h. 41m. lis. ; Dec. N. 35° 54' 03". A 5, B 10, and C 6, all bluish. 

6. f.i Cygni — A beautiful double star, with a distant companion, on the very tip of the 
right wing; R. A. 21h. 36m. 59s.; Dec. N. 28° 01' 04". A 5, white; B 6, and C 7%, 
both blue. 

7. A binary star (61 Cygni) — the most remarkable known in the heavens. It is situ- 
ated on the inner tip of the right wing of Cygni, 7%° south-by-east of Deneb, and nearly 
east of Vega ; R. A. 20h. 59m. 43s. ; Dec. N. 37° 58' 0". A 5%, and B 6, both yellow, but 
the latter of the deepest tint. From the great rapidity of its proper motion, this star is 
regarded as one of the nearest to our system. It affords a positive instance of a double 
star which, besides the individuals revolving round each other, or about their common 
center of gravity, has a progressive uniform motion towards some determinate region. It is 
supposed to be not less than 412,000 times the diameter of the earth's orbit from us ; or 
38,190,000,000,000 miles distant ; and to be moving through space 60,000 times as fast as 
Mercury — the swiftest body known to our system. The period of 61 Cygni as a binary 
system, is about 450 years. For orbit, &c, see Map VIII., Fig. 18, and 19. 

8. A fine double star on the tip of the left wing, 10° northwest of a Cygni, and within 
1° of 6; R. A. 19h. 37m. 34s. ; Dec. N. 50° 09' 3". A 6% and B 7, both pale fawn color. 

9. A wide quadruple star in a rich field, on the Swan's left thigh, about 8° west by 
north of Deneb ; R. A. 20h. 08m. 36s. ; Dec. N. 46° 15' 6". A 4, orange ; B 16, livid ; C 7>g, 
and D 53^, both cerulean blue. Not the effect of contrast. 

10. A neat small cluster in the root of the neck, about 2° south of y; R. A. 20h. 18m. 
17s. ; Dec. N. 37° 59' 9". A 8, yellow; B 11, dusky. 

11. A loose splashy cluster in a rich vicinity, between the Swan's tail and the Lizard, 
due south of (3 Cephei, and east-northeast of Deneb ; R. A. 21h. 26m. 29s. ; Dec. N. 47* 
43' 8'. 

Telescopic Objects. — Alpha? Beta? Delta? Zeta? Lambda? Mu? What cele- 
brated binary star? Remarks respecting? Period? Point out on the map. What 
other double star ? Quadruple? What clusters ? Nebula? 



CAPRICORNUS. 127 

12. Avert singular nebula on the tip of the northern wing, about 5%* north of 
6 ; R. A. 19h. 40m. 35s. ; Dec. N. 50° 07' 6". Seen to be nebulous only with good instru- 
ments. Several telescopic stars in the field. The Herschels considered this as a con 
necting link between planetary nebula and nebulous stars. 



CAPRICORNUS (the goat).- MAP V. 

229. This is the tenth sign, and eleventh constellation, in the 
order of the Zodiac, and is situated south of the Dolphin, and 
next east of Sagittarius. Its mean declination is 20° south, and 
its mean right ascension 310°. It is therefore on the meridian 
about the 18th of September. It is to be observed that the 
first point of the sign Capricorn, not the constellation, marks the 
southern tropic, or winter solstice. The sun, therefore, arrives 
at this point of its orbit the 21st of December, but does not 
reach the constellation Capricorn until the 16th of January. 

The sun, having now attained its utmost declination south, after remaining a few days 
apparently stationary, begins once more to retrace its progress northwardly, affording to 
the wintry latitudes of the north a grateful presage of returning spring. 

At the period of the winter solstice, the sun is vertical to the tropic of Capricorn, and 
the southern hemisphere enjoys the same light and heat which the northern hemisphere 
enjoys on the 21st of June, when the sun is vertical to the tropic of Cancer. It is, at 
this period, mid-day at the south pole, and midnight at the north pole. 

230. The whole number of stars in this constellation is fifty- 
one ; none of which are very conspicuous. The three largest 
are only of the 3d magnitude. There is an equal number of 
the 4th. 

The head of Capricorn may be recognized by means of two 
stars of the 3d magnitude, situated a little more than 2° apart, 
called Giedi and JDabik. They are 28° from the Dolphin, in a 
southerly direction. 

Giedi is the most northern star of the two, and is double. Tf a line be drawn from 
Lyra through Altair, and produced about 23° farther, it will point out the head of Capri- 
corn. These two stars come to the meridian the 9th of September, a few minutes after 
Sad'r, in Cygnus. A few other stars of inferior note may be traced out by reference to 
the maps. 

The sign of the Goat was called by the ancient orientalists the " Southern gate of the 
Sun," as Cancer was denominated the "Northern gate." The ten stars in the sign 
Capricorn, known to the ancients by the name of the " Tower of Gad," are probably now 
in the constellation Aquarius. 

HISTORY. 

Capricornus is said to be Pan, or Bacchus, who, with some other deities, were feasting 
near the banks of the Nile, when suddenly the dreadful giant Typhon came upon them, 
and compelled them all to assume a different shape, in order to escape his fury. Ovid 
relates, 

" How Typhon, from the conquer'd skies, pursued 
Their routed godheads to the seven-mouth'd flood : 

229. Position of Capricornus? When does the sun enter it? What said of his place 
and motion at that time? Of the winter solstice? 230. Number of stars in Capri- 
corn? Their magnitudes? How recognize the figure? What said of Giedi? Ancient 
name of this sign ? 



128 ASTRONOMY. 

Forced every god (his fury to escape), 
Some beastly form to take, or earthly shape. 
• Jove (sings the bard) was changed into a ram, 
From whence the horns of Libyan Ammon came ; 
Bacchus a goat ; Apollo was a crow ; 
Phoebe a cat ; the wife of Jove a cow, 
Whose hue was whiter than the falling snow; 
Mercury to a nasty ibis turned — 
While Venus from a fish protection craves, 
And once more plunges in her native waves." 

On this occasion it is further related that Bacchus, or Pan, led the way and plunged 
into the Nile, and that the part of his body which was under the water assumed the form 
of a fish, and the other part that of a goat; and that to preserve the memory of this 
frolic, Jupiter made him into a constellation, in his metamorphosed shape. 

Some say that this constellation was the goat Amalthea, who supported the infant 
Jupiter with her milk. To reward her kindness, the father of the gods placed her cimomj 
the constellations, and gave one of her horns to the nymphs who had taken care of him 
in his infantile years. This gift was ever after called the horn of plenty; as it possessed 
the virtue of imparting to the holder whatever she desired. On this account the Latin 
term Cormtcopia, denotes plenty, or abundance of good things. The word Amalthea, 
when used figuratively, has also the same meaning. 

The real sense of this fable, divested of poetical embellishment, appears to be this ; 
that in Crete, some say in Libya, there was a small territory shaped very much like a 
bullock's horn, and exceedingly fertile, which the king presented to his daughter Amal- 
thea, whom the poets feigned to have been Jupiter's nurse. 

" The bounteous Pan," as he is styled by Milton, was the god of rural scenery, shep- 
herds, and huntsmen. Virgil thus addresses him : — 

"And thou, the shepherd's tutelary god, 
Leave, for a while, Pan 1 thy loved abode." 

The name of Pan is derived from a Greek word signifying all things ; and he was often 
considered as the great principle of vegetable and aniasal life. He resided chiefly in 
Arcadia, in woods and the most rugged mountains. As Pan usually terrified the inhabi- 
tants of the adjacent country, even when he was nowhere to be seen, that kind of fear 
which often seizes men, and which is only ideal or imaginary, has received from him the 
name of Panic. 

Pales, the female deity corresponding to Pan, was the goddess of sheepfolds and of 
pastures among the Romans. Thus Virgil : — 

" Now, sacred Pales, in a lofty strain, 
I sing the rural honors of thy reign." 

The shepherds offered to this goddess milk and honey, to gain her protection over their 
flocks. She is represented as an old woman, and was worshiped with great solemnity 
at Rome. Her festivals, which were called Pulilia, were celetrated on the 20th of April, 
the day on which Romulus laid the foundations of the city. 

TELESCOPIC OBJECTS. 

1. a Capricorni— A quintuple star in the right horn ; R. A. 20h. 09m. 10s. ; Dec. S. 13° 
02' 1". A 3, pale yellow; B (or a 1) 4, yellow ; C 16, blue ; D 9, ash-colored; E 9%, lilac 
tinge. Few telescopes will reveal all these components. 

2. (3 Capricorni — A wide pair of stars in the right horn, 2H° south-half-east of a; 
R. A. 20h. 12m. 01s. ; Dec. S. 15° 16' 9". A 3%, orange yellow; B 7, sky blue. Other 
small stars in the field. It requires, a powerful instrument, and the most favorable cir- 
cumstances to detect the minute star 5. (See Map VIII. , Fig. 20.) 

3. A globular cluster between Aquarius and the neck of Capricorn, 9° due east of 
a Capricorni, about %' from a 8th magnitude star; R. A. 20h. 44m. 39s. ; Dec. S. 13° 07' 
6". Many stars in the field, two of which are close to the cluster, or the east. Map IX., 
Fig. 63. 

History. — Who was Capricornus ? What proof cited ? What further? What other 
mvth ? Meaning of this fable ? What said of Pales? 

Tklescopic Objects.— Alpha? Beta? Point out on the map? What clusters ? Where 
shown on the map ? 



PEGASUS 129 

4. A fine pale white cluster, about 20° west-northwest of Fomalhaut; R. A. 21h. 
81m. 16s. ; Dec. S. 23° 52' 4"- A bright object, with straggling streams of stars, and but 
few outliers in the field. Seen with small instruments. Map IX., Fig. 64. 



CHAPTER XII. 

CONSTELLATIONS ON THE MERIDIAN IN OCTOBER. 

PEGASUS (the plying horse).— MAP II. 

231. This constellation is represented in an inverted posture, 
with wings. It occupies a large space in the heavens, between 
the Swan, the Dolphin and the Eagle, on the west, and the Nor- 
thern Fish and Andromeda, on the east. Its mean right ascen- 
sion is 340°, or it is situated 20° W. of the prime meridian. It 
extends from the equinoctial N. 35°. Its mean length E. and 
W. is about 40°, and it is six weeks in passing our meridian, 
viz., from the 1st of October to the 10th of November. 

232. We see but a part of Pegasus, the rest of the animal 
being, as the poets imagined, hid in the clouds. It is readily 
distinguished from all other constellations by means of four 
remarkable stars, about 15° apart, forming the figure of a square 
called the Square of Pegasus. 

The two western stars in this square come to the meridian about the 23d of October, 
and are 13° apart. The northern one, which is the brightest of three triangular stars 
in the martingale, is of the 2d magnitude, and is called Scheat. Its declination is 26%°. 
ifarkab, also, of the 2d magnitude, situated in the head of the wing, is 13° S. of Scheat, 
and passes the meridian 11 minutes after it. 

The two stars which form the eastern side of the square, come to the meridian about 
an hour after those in the western. The northern one has already been described as 
Alpheratz in the head of Andromeda, but it also belongs to this constellation, and is 14° 
E. Scheat. 14' S. of Alpheratz, is Algenib, the last star in the wing,situated 16j£° E. of 
Markab. 

233. Algenib in Pegasus, Alpheratz in Andromeda, and Caph 
in Cassiopeia are situated on the prime meridian, and point out 
its direction through the pole. For this reason they are some- 
times called the three guides. They form an arc of that great 
circle in the heavens from which the distances of all the heavenly 
bodies are measured. 

231. What constellations in this chapter? Describe Pegasus, its size, position, &c. 
232. Do we see the whole of the figure ? How is it distinguished ? What said of Scheat 
and Markab? Of Alpheratz and Algenib? 233. Remark respecting Algenib, Alphe- 
ratz and Caph? What sometimes called, and why? They form what? Remprks 



130 ASTRONOMY. 

It is an arc of the equinoctial colure which passes through the vernal equinox, and 
.which the sun crosses about the 21st of March. It is, in astronomy, what the meridian 
of Greenwich is in geography. If the sun, or a planet, or a star, be said to have so many 
degrees of right ascension, it means that the sun or planet has ascended so many degrees 
from this prime meridian. 

Enif, sometimes called Enir, is a star of the 3d magnitude in the nose of Pegasus, 
about 20° W. S. W. of Markab, and half-way between it and the Dolphin. About half of 
the distance from Markab toward Enif, but a little to the S., there is a star of the 3d mag- 
nitude situated in the neck, whose letter name is Zeta. The loose cluster directly S. of 
the line joining Enif and Zeta, forms the head of Pegasus. 

In this constellation there are eighty-nine stars visible to the naked eye, of which three 
are of the second magnitude and three of the third. 

HISTORY. 

This, according to fable, is the celebrated horse which sprung from the blood of Medusa, 
after Perseus had cut off her head. He received his name according to Hesiod, from his 
being born near the sources (TC?]y>], Pege) of the ocean. According to Ovid, he fixed his 
residence on Mount Helicon, where, by striking the earth with his foot, he raised the 
fabled fountain called Hippocrene. He became the favorite of the Muses ; and being 
tamed by Neptune or Minerva, he was given to Bellerophon, son of Olaucus, king of 
Ephyre, to aid him in conquering the Chkusera, a hideous monster that continually vom- 
ited flames. This monster had three heads, that of a lion, a goat, and a dragon. The 
fore parts of its body were those of a lion, the middle those of a goat, and the hinder 
those of the dragon. It lived in Lycia, of which the top, on account of its desolate wil- 
derness, was the resort of lions, the middle, which was fruitful, was covered with goats, 
and at the bottom, the marshy ground abounded with serpents. Bellerophon was the 
first who made his habitation upon it. 

Plutarch thinks the Chimsera was the captain of some pirate who adorned their ship 
with the images of a lion, a goat, and a dragon. 

After the destruction of this monster, Bellerophon attempted to fly up to heaven upon 
Pegasus; but Jupiter was so displeased at this presumption, that he sent an insect to 
sting the horse, which occasioned the melancholy fall of his rider. Bellerophon fell to 
the earth, and Pegasus continued his flight up to heaven, and was placed by Jupiter 
among the constellations. 

" Now heav'n his further wand'ring flight confines, 
Where, splendid with his num'rous stars, he shines." 

Ovid's Fasti. 

TELESCOPIC OBJECTS. 

1. a Pegasi (Markab) — A star with a distant companion, at the junction of the wing 
and shoulder, 13" south of Scheat ; R. A. 22h. 56m. 47s. ; Dec. N. 14° 20' 08°. A 2, white ; 
B 11, pale grey. 

2. (3 Pegasi (SoJieat) — A bright star with a minute distant companion, on the left fore- 
leg; R. A. 22h. 56m. 01s. ; Dec. N. 27° 13' 0". A 2, deep yellow ; B 15, blue ; with two 
other stars in the field. 

3. y Pegasi (AlgeniU) — A star with a distant companion, on the edge of the wing; 
R. A. Oh. 05m. 0s. ; Dec. N. 14° 17' 07". A 2%, yellow ; B 13, pale blue. 

4. e Pegasi (Enif) — A star with two distant companions, in the nose of the figure ; 
R. A. 21h. 36m. 19s. ; Dec. N. 9° 08' 07". A 2%, yellow ; B 14, blue ; C 9, violet; and a 
9th magnitude star of a violet tinge, at a distance east. 

5. C, Pegasi — A star with a minute companion in the middle of the neck ; R. A. 22h. 33m- 
29s.; Dec. N. 9° 59' 9". A line from Alpheratz over Markab, and carried 7° further, will 
reach f. A3, light yellow; B 13, dusky; with other stars in the field. 

6. A double star between the head of Pegasus and the hind legs of the Fox ; or about 
10^° south by east of C, Cygni ; R. A. 21h. 14m. 41s. ; Dec. N. 19° 07' 4". A 4, pale orange, 
and considered variable ; B 9, purplish. 

respecting the prime meridian ? What said of Enif? Of Zeta ? Of the head of Pegasus 
Number of stars in the constellation, and their magnitudes ? 

History.— Story of his origin and name? Residence, &c. ? How he earae among the 
stars ? 

Telescopic Objects.— Alpha? Beta? Gamma? Epsilon? Zeta? What double star? 
What cluster ? Point out on the map. What nebula? 



AQUARIUS. 131 

7. A globular cluster between the mouths of Pegasus and Equleus, about 4° north- 
west of £ ; R. A. 21h. 22lo. VSs. ; Dec. N. 11° 27' 4". Map IX., Fig. 65. It is laid down as 
a nebula on Map II., but with a good instrument it is resolved into stars, with straggling 
outliers, as shown in the diagram. 

8. An elongated nebula in the animal's mane, about 3° due south of Markab ; R. A. 
22h. 56m. 58s. ; Dec. N. 11° 27' 9". A very faint and difficult object. 



EQULEUS, VEL EQUI SECTIO (the little horse, or the 
horse's head). — MAP II. 

234. This Asterism, or small cluster of stars, is situated about 
1° W. of Enif, in the head of Pegasus, and about half-way 
between it and the Dolphin. It is on the meridian at 8 o'clock, 
on the 11th of October. It contains ten stars, of w r hich the 
four principal are only of the 4th magnitude. These may be 
readily distinguished by means of the long irregular square 
which they form. The two in the nose are much nearer together 
than the two in the eyes : the former being 1° apart, and the 
latter 2^°. Those in the nose are uppermost, being 4° N. of 
those in the eyes. This figure also is in an inverted position. 
These four stars are situated 10° or 12° S. E. of the diamond 
in the Dolphin's head. Both of these clusters are noticeable on 
account of their figure rather than their brilliancy. 

history. 

This constellation is supposed to be the brother of Pegasus, named Ceteris, given by Mer- 
cury to Castor, who was so celebrated for his skill in the management of horses ; others 
take him to be the celebrated horse which Neptune struck out of the earth with his tri- 
dent, when he disputed with Minerva for superiority. The head only of Celeris is 
visible, and this, also, is represented in an inverted position. 

TELESCOPIC OBJECTS.- 

Four of the principal stars in this little group are double — namely, 8, J, £ and "k. 8 
is rather a star with a companion ; R. A. 21h. 14m. 57s. ; Dec. N. 6° 07' 9". The other 
three will easily be found from their proximity to 8. 



AQTTAKiUS (the water-bearer). — MAP II. 

235. This constellation is represented by the figure of a 
man pouring out water from an urn. It is situated in the Zodiac, 
immediately S. of the equinoctial, and bounded by the Little 

234. Situation of Equleus ? When on the meridian ? Number of stars, and how dia* 
tinguished? What further description ? 

History. — What suppositions respecting the origin of Eqiileus ? 
Telescopic Objects. — What double stars ? How found ? 

235. How is Aquarius represented? Its boundaries ? 



6* 



132 ASTRONOMY. 

Horse, Pegasus, and the Western Fish on the N., the Whale on 
the E., the Southern Fish on the S. and the Goat on the W. 

236. Aquarius is now the 12th in order, or last of the 
Zodiacal constellations ; and is the name of the 11th sign in the 
ecliptic. Its mean declination is 14° S., and its mean right 
ascension 335°, or 22 hours, 20 min. ; it being 1 hour and 40 
min. W. of the equinoctial colure ; its center is, therefore, on 
the meridian the 15th of October. 

It contains one hundred and eight stars ; of which the four 
largest are all of the 3d magnitude. 

"His head, his shoulders, and his lucid hreast, 
Glisten with stars ; and where his urn inclines, 
Rivers of light brighten the watery track." 

237. The northeastern limit of Aquarius may be readily dis- 
tinguished by means of four stars of the 4th magnitude, in the 
hand and handle of the urn, so placed as to form the letter Y, 
very plainly to be seen, 15° S. E. of Enif, or 18° S. S. W. of 
Markab, in Pegasus ; making with the two latter nearly a right 
angle. 

About 4H° W. of the figure is El Melik, a star of the 3d magnitude, in the E. shoulder, 
and the principal one in this constellation. 10° S. W. of El Melik, is another star of the 
same magnitude, situated in the W. shoulder, called Sad es Saud. 

Ancha, of the 4th magnitude, is in the right side, 8° S. of El Melik. 9° E. of Ancha, is 
another star of the 4th magnitude, whose letter name is Lambda. 

Scheat, of the 3d magnitude, lying below the knee, is situated 833* S. of Lambda; and 
14° S. of Scheat, the brilliant star Fomalhaut, of between the 1st and 2d magnitudes, ter- 
minates the cascade in the mouth of the Southern Fish. This star is common to both 
these constellations, and is one of those from which the lunar distance is computed for 
ascertaining the longitude at sea. It culminates at 9 o'clock on the 22d of October. 

Fomalhaut, Deneb Kaitos, and Alpha in the head of the Phoenix, make a large triangle, 
whose vertex is in Deneb Kaitos. Those two stars of the fourth magnitude, situated 4° 
S. of Sad es Saud, and nearly the same distance from Ancha, are in the tail of Capricorn. 
They are about 2° apart. The western one is called Deneb Algedi. 

The rest of the stars in the cascade are quite small; they maybe traced from the 
letter Y, in the urn, in a southeasterly direction toward the tail of Cetus, from which the 
cascade suddenly bends off near Scheat, in an opposite course, and finally disappears in 
the mouth of the Southern Fish, 30° S. of Y. 

HISTORY. 

This constellation is the famous Ganymede, a beautiful youth of Phrygia, son of Tros, 
king of Troy, or, according to Lucian, son of Dai'danus. He was taken up to heaven by 
Jupiter as he was tending his father's flocks on Mount Ida, and became the cup-bearer 
of the gods in place of Hebe. There are various opinions, however, among the ancients 
respecting its origin. Some suppose it represents Deucalion, who was placed among the 
stars after the celebrated deluge of Thessaly, 1500 years before the birth of our Saviour ; 
while others think it designed to commemorate Cecrops, who came from Egypt to Greece, 
founded Athens, established science, and introduced the arts of polished life. 

The ancient Egyptians supposed the setting or disappearance of Aquarius caused the 
Nile to rise, by the sinking of his urn in the water. In the Zodiac of the Hebrews, 
Aquarius represents the tribe of Reuben. 

Its order in the signs and constellations ? Number and size of its stars ? 237. How 
distinguish the northeast limit? What said of El Melik? Of Sad es Saud? Of Ancha, 
Lambda, Scheat, &c. 

History. — Story of Ganymede, and Jupiter? What other myth? Idea of the Egyp 
tains ? Hebrew Zodiac ? 



PISCES AUSTRALIS. 133 



TELESCOPIC OBJECTS. 

1. a Aquarii {Phard) — A star with a minute companion on the Water-bearer's left 
shoulder; R. A. 2 In. 57m. 33s. ; Dec. S. 1° 05' 07". A 3, pale yellow; B 13, grey; and 
another star in the field on a line with A and B. Markab is on a line joining Alpheratz 
and Phard, and about half way between them. 

2. Aquarii {Sad-al-melik) — A star with a companion on the right shoulder ; R. A. 
21h. 23m. 07s. ; Dec. N. 6° 16' 04". A 3, pale yellow; B 15, blue. A very delicate object. 

3. y Aquarii — A delicate but wide double star, on the water-pot; R. A. 22h. 13m. 
23s. ; Dec. S. 2° 11' 05". A 4, greenish tinge ; B 14, purple. It is about 4° east-by-south 
from Sad-al-melik. 

4. C, Aquarii — A binary star in the left wrist, about 6° east from Sadalmeiik; R. A. 
22h. 20m. 35s. ; Dec. S. 0° 50' 02". A 4, very white ; B 4%, white. 

5. r' Aquarii — A fine double star in the left leg, one third of the way from Fomalhaut 
to f Pegasi; R. A. 22h. 39m. 13s. ; Dec. S. 14° 53' 09". A 6, white ; B 9%, pale garnet. 

6. i/>' Aquarii — A double star in the stream, being the first of three similar stars 
marked tyi, ^, -03; R. A. 23h. 07m. 30s.; Dec. S. 9° 57' 05". A5%, orange tint; B 9, sky 
blue. It is about one-third of the way from Fomalhaut to a Andvomedse. Several other 
beautiful double stars east of Scheat, in the stream, as shown on the map. 

7. A fine globular cluster near the neck of Aquarius, about 5° north-half-east from 
/?; R. A. 21h. 23m. 07s. ; Dec. S. 6° 16' 04". A cluster of exceedingly small stars, which 
has been likened to " a heap of fine sand." Several telescopic outliers in the field. Map 
VIII. , Fig. 66. 

8. A planetary nebula in the middle of the scarf; R. A. 20h. 55m. 27s.; Dec. S. 11* 
59' 03". About 12° east of a Capricorni, where a line from the Eagle's tail over d Anti- 
noi, and as far again, reaches it. It is bright to its very disc, and but for its pale blue 
tint, would be a very miniature of Venus. 



PISCES AUSTEALIS (the southern fish).— MAP II. 

238. This constellation is directly S. of Aquarius, and is 
represented as a fish drinking the water which Aquarius pours 
from his urn. Its mean declination is 31° S. and its mean right 
ascension and time of passing the meridian are the same as those 
of Aquarius, and it is seen on the meridian at the same time, 
viz. on the 15th of October. It contains 24 visible stars, of 
which one is of the 1st magnitude, or between the 1st and 2d, two 
are of the 3d, and five of the 4th. The first and most beautiful 
of all is Fomalhaut, situated in the mouth. This is 14° directly 
S. of Scheat in Aquarius, and may be seen passing the meridian 
low down in the southern hemisphere, on the 22d and 23d of 
October. Its position in the heavens has been determined with 
the greatest possible accuracy, to enable navigators to find their 
longitude at sea. 

The mode of doing this cannot be explained here. The problem is one of some difficulty. 
It consists in finding the angular distance between some star whose position is well known, 

Telescopic Objects. — Alpha? Beta 2- Gamma? Zeta? Tau? Psi? What clusters, 
and where shown on the map ? What nebula? 

238. Situation of Pisces Australis ? How represented ? When on the meridian ? Num- 
ber of stars? Magnitude? The principal star ? How situated? What use made of it? 
What said of the method of finding the longitude by the moon and stare ? 



134 ASTRONOMY. 

and the moon when she is passing near it; also, the altitude of each, at the same instant, 
with good sextants. These data furnish the elements of a spherical triangle, the solution 
of which, after various intricate corrections, is made to result in the longitude of the given 
place. — See note to Arietes. In 1714, the British Parliament offered a reward of 10,000 
pounds sterling, to any man who should discover a method of determining the longitude 
within 1°, or 60 geographical miles of the truth ; 15,000 pounds to the man who should 
find it within 40 miles, and 20,000 pounds, if found within 80 miles. These rewards in part, 
have been since distributed among eminent mathematicians, in Europe, agreeably to the 
respective merits of their discoveries. 

HISTORY. 

This constellation is supposed to have taken its name from the transformation of Venus 
into the shape of a fish, when she fled, terrified at the horrible advances of the monster 
Typhon, as we have related in the mythology of the Fishes. — (See Pisces.) 

TELESCOPIC OBJECTS. 

a Pisces Australts — A first magnitude star with a very distant companion, in the eye 
of the fish ; R. A. 22h. 48m. 48s. ; Dec. S. 30° 28' 03'. A 1, reddish ; B 9%, dusky blue. 



LACERTA (the lizard).— MAP II. 

239. This is a small and obscure modern constellation, between 
the tail of Cygnus and the head of Andromeda. It has one star 
of the 4th magnitude, eight of the 5th, and a few much smaller. 

240. Between Lacerta and Andromeda a singular looking 
figure appears on the map, called Gloria Frederica ; or Frederics 
Glory. It was inserted among the constellations by Bode, in 
178T, as a compliment to Frederic II., of Prussia. It consists 
of a crown, a laurel, a sword, and a pen, to represent the mon- 
arch, the hero, the sage, and the pacificator. But the constel- 
lation was not recognized by astronomers, and, as such, has 
already passed from the heavens. 

TELESCOPIC OBJECTS. 

1. A neat double stab on the tip of the Lizard's tail ; R. A. 22h. 11m. 56s. ; Dec. N. 
86° 58' 01". A 6%, pale white ; B 9, livid. 

2. A delicate but wide double stab on the shoulder ; R. A. 22h. 14m. 25s. ; Dec. N. 45° 
43' 09". A 5, pale yellow; B 13, orange tint. A line from Polaris carried by the east of 
Cepheus tiara, and 11° further, will find it the lucida of a fine galaxy field. 

3. A wide double stab near the end of the tail, the southern star of three forming a 
neat triangle ; R. A. 22h. 32m. 05s. ; Dec. N. 3S° 13' 2". A 6%, white ; B 10, violet. 

4. A delicate tbiple star in the space between the Lizard's back and the left hand of 
Andromeda; R. A. 22h. 49m. 06s.; Dec. N. 40° 45' 1". A 6, bright white; B. 15, pale 
blue; C 9%, reddish; a fourth star at a distance. A very difficult object; claimed by 
some for Andromeda, but usually classed as belonging to the Lizard. 

Histoby. — Supposed origin of this constellation ? 

Telescopic Objects. — Alpha? Where situated? 

239. Describe Lacerta. Where situated ? 240. What other small constellation near ? 
By whom inserted, when and why? Of what does it consist? To represent what? Is it 
recognized by astronomers 1 

Telescopic Objects. — What double stars in Lacerta? What triple star ? Quadruple? 
Cluster ? Any of them shown on the map ? 



VARIABLE AND DOUBLE STARS. 135 

5. A quadruple star, the western one of the three forming the triangle at the end of 
the tail ; R. A. 22h. 29m. 46s. ; Dec. N. 38° 48' 5". About 20° northwest of Alpheratz. A 
and B 6%, both white ; C 11, greenish ; D 10, blue. 

6. A large loose cluster in the Lizard's mouth ; R. A. 22h. 08m. 59s. ; Dec. N. 49° 05' 
1". Stars from the 9th to the 14th magnitudes. A line carried from Polaris through the 
tiara of Cepheus, and 8° beyond, strikes it. 



CHAPTER XIII. 

VARIABLE AND DOUBLE STARS— CLUSTERS AND 
NEBULAE. 

241. The periodical variations of brilliancy to which some of 
the fixed stars are subject, may be reckoned among the most 
remarkable of their phenomena. Several stars, formerly distin- 
guished by their splendor, have entirely disappeared ; others are 
now conspicuous which do not seem to have been visible to the 
ancient observers ; and there are some which alternately appear 
and disappear, or, at least, of which the light undergoes great 
periodic changes. Some seem to become gradually more 
obscure, as Delta in the Great Bear ; others, like Beta in the 
Whale, to be increasing in brilliancy. 

242. Some stars have all at once blazed forth with great splen- 
dor, and, after a gradual diminution of their light, again become 
extinct. The most remarkable instance of this kind is that of 
the star which appeared in 1572, in the time of Tycho Brahe. 
It suddenly shone forth in the constellation Cassiopeia, with a 
splendor exceeding that of stars of the first magnitude, even of 
Jupiter and of Venus, at their least distances from the earth ; 
and could be seen with the naked eye, on the meridian, in full 
day! Its brilliancy gradually diminished from the time of its 
first appearance, and at the end of sixteen months it entirely 
disappeared, and has never been seen since. (See a more, par- 
ticular account of this phenomenon, page 35. J 

Another instance of the same kind was observed in 1604, when a star of the first mag- 
nitude suddenly appeared in the right foot of Ophiuchus. It presented, like the former, 
all the phenomena of a prodigious flame, being, at first, of a dazzling white, then of a 
reddish yellow, and, lastly, of a leaden paleness ; in which its light expired. These 
instances prove that the stars are subject to great physical revolutions. {Page n0) 

243. A great number of stars have been observed whose light 
seems to undergo a regular periodic increase and diminution. 

241. What said of the periodical variations of the stars ? 242. What other remarka- 
ble phenomenon? What instances cited? What do these instances prove? 243. What 



136 ASTRONOMY. 

They are properly called Variable Stars. One in the Whale has 
a period of 344 days, and is remarkable for the magnitude of its 
variations. From being a star of the second magnitude, it 
becomes so dim as to be seen with difficulty through powerful 
telescopes. Some are remarkable for the shortness of the period 
of their variation. Algol has a period of between two and three 
days ; Delta Cephei, of 5-J- days ; Beta Lyra, of 6 2-5 days ; 
and Mn Antinoi, of 7 days. 

The regular succession of these variations precludes the supposition of an actual 
destruction of the stars; neither can the variations be supposed to arise from a change 
of distance ; for, as the stars invariably retain their apparent places, it would be neces- 
sary to suppose that they approach to, and recede from the earth in straight lines, 
which is very improbable. The most probable supposition is, that the stars revolve, like 
the sun and planets, about an axis. " Such a motion," says the elder Herschel, " may 
be as evidently proved, as the diurnal motion of the earth. Dark spots, or large por- 
tions of the surface, less luminous than the rest, turned alternately in certain directions, 
either toward or from us, will account for all the phenomena of periodical changes in the 
luster of the stars, so satisfactorily, that we certainly need not look for any other cause.'' 

DOUBLE STAKS. 

244. On examining the stars with telescopes of considerable 
power, many of them are found to be composed of two or more 
stars, placed contiguous to each other, or of which the distance 
subtends a very minute angle. This appearance is, probably, in 
many cases, owing solely to the optical effect of their position 
relative to the spectator ; for it is evident that two stars will 
appear contiguous if they are placed nearly in the same line of 
vision, although their real distance may be immeasurably great. 

STARS OPTICALLY DOUBLE. 

Apparent position. True position. 
* 

£„„=— „ ^ 

A B 

Here the observer on the left sees a large and small star at A, apparently near toge- 
ther — the lowest star being much the smallest. But instead of their being situated as 
they appear to be, with respect to each other, the true position of the smaller star may 
be at B instead of A; and the difference in their apparent magnitudes may be wholly 
owing to the greater distance of the lower star. 

Upon this subject Dr. Herschel remarks, that this nearness of the stars to each other, 
in certain cases, might be attributed to some accidental cause, did it occur only in a few 
instances ; but the frequency of this companionship, the extreme closeness, and, in 
many cases, the near equality of the stars so conjoined, would alone lead to a strong 
suspicion of a more near and intimate relation than mere casual juxtaposition. 

245. There are, however, many instances in which the angle 
of position of the two stars varies in such a manner as to indi- 

are these unsteady stars called ? What specimens referred to, and their periods? What 
does this regular succession, &c, prove? What theory did Dr. Herschel adopt respect- 
ing the variable stars? 244. What said of double stars? Are they always really near 
each other? Illustrate on blackboard. Remark of Dr. Herschel? 245. Are they 



STARS OPTICALLY DOUBLE. 13? 

cate a revolution about each other and about a common center. 
In this case they are said to form a Binary system performing to 
each other the office of sun and planet, and are connected 
together by laws of gravitation like those which prevail in the 
solar system. 

The recent observations of Sir John Herschel and Sir James South, have established the 
truth of this singular fact beyond a doubt. Motions have been detected, so rapid as to 
become measurable within very short periods of time; and at certain epochs, the satellite 
or feebler star has been observed to disappear, either passing behind or before the primary, 
or approaching so near to it that its light has been absorbed by that of the other. 

246. The most remarkable instance of a regular revolution of 
this sort, is that of Mizar, in the tail of the Great Bear ; in 
which the angular motion is 6 degrees and 24 minutes of a great 
circle, annually ; so that the two stars complete a revolution 
about one another in the space of 58£ years. About eleven- 
twelfths of a complete circuit have been already described since 
its discovery in 1781, the same year in which the planet Herschel 
was discovered. 

A double star in Ophiuchus presents a similar phenomenon, and 
the satellite has a motion in its orbit still more rapid. Castor 
in the Twins, Gamma Virginis, Zeta in the Crab, Zi Bootis, 
Delta Serpentis, and that remarkable double star 61 Cygni, 
together with several others, amounting to 40 in number, exhi- 
bit the same evidence of a revolution about each other and about 
a common center. (For a more particular description of these 
stars, see Telescopic Objects and the Map.) 

But it is to be remembered that these are not the revolutions of bodies of a planetary 
nature around a solar center, but of sun around sun — each, perhaps, accompanied by its 
train of planets, and their satellites, closely shrouded from our view by the splendor of 
their respective suns, and crowded into a space bearing hardly a greater proportion to 
the enormous interval which separates them,, than the distances of the satellites of our 
planets from their primaries bear to their distances from the sun itself. 

247. The examination of double stars was first undertaken by 
the late Sir William Herschel, with a view to the question of 
parallax. His attention was, however, soon arrested by the 
new and unexpected phenomena which these bodies presented. 

Sir William observed of them, in all, 2400. Sir James South and Herschel have given a 
catalogue of 380 in the Transactions of the Royal Society for 1824, and South added 458 
in 1826. Sir John Herschel, in addition to the above, published an account of 1000, before 
he left England for the Cape of Good Hope, where he went to push his discoveries in the 
southern hemisphere. Professor Struve, with the great Dorpat telescope, has given a 
catalogue of 3,063 of the most remarkable of these stars. 

The object of these catalogues is not merely to fix the place of the star within such limits 
as will enable us easily to discover it at any future time, but also to record a description 

ever really near each other? What motion? What do these constitute? Is it certain 
that stars are ever thus in motion around a common center ? 246. What remarkable 
instance cited? Its annual angular motion? Period? What other binary systems? 
Are these planetary systems like our own ? 247. Who first undertook the examination 
of the double stars, and with what view ? What number did ha observe? What cata- 



138 ASTRONOMY. 

of the appearance, position, and mutual distances of the individual stars composing tne 
system, in order that subsequent observers may have the means of detecting their con- 
nected motions, or any changes which they may exhibit. Professor Struve has also taken 
notice of 52 triple stars, among which No. 11 of the Unicom, Zeta of Cancer, and Zi of 
the Balance, appear to be ternary systems in motion. Quadruple "and quintuple stars 
have likewise been observed, which also appear to revolve about a common center of 
gravity ; in short, every region of the heavens furnishes examples of these curious phe- 
nomena. 

COLOR OF THE STARS. 

248. Many of the double stars exhibit the curious and beau- 
tiful phenomenon of contrasted colors, or complimentary tints. In 
such instances, the larger star is usually of a ruddy or orange 
hue, while the smaller one appears blue or green, probably in 
virtue of that general law of optics, which provides that when 
the retina is under the influence of excitement by any bright 
colored light, feebler lights, which, seen alone, would produce no 
sensation but that of whiteness, shall for the time appear 
colored with the tint complimentary to that of the brighter. 

Thus, a yellow color predominating in the light of the brighter star, that of the less 
bright one, in the same field of view, will appear blue ; while, if the tint of the brighter 
star verge to crimson, that of the other will exhibit a tendency to green — or even appear 
a vivid green. The former contrast is beautifully exhibited by Iota, in Cancer ; the latter 
by Almaack, in Andromeda — both fine double stars. If, however, the colored star be 
much the less bright of the two, it will not materially affect the other. Thus, for instance, 
Eta Cassiopeise exhibits the beautiful combination of a large white star, and a small one 
of a rich ruddy purple. 

249. It is not easy to conceive what variety of illumination 
two suns — a red and a green, or a yellow and a blue one — must 
afford to a planet revolving about either ; and what charming 
contrasts and grateful vicissitudes — a red and a green day, for 
instance, alternating with a white one and with darkness — might 
arise from the presence or absence of one or the other, or both, 
above the horizon. 

Insulated stars of a red color, almost as deep as that of blood, occur in many parts of 
the heavens, but no green or blue star (of any decided hue) has, we believe, ever been 
noticed, unassociated with a companion brighter than itself. 



CLUSTERS OF STARS. 

250. When we cast our eyes over the concave surface of the 
heavens in a clear night, we do not fail to observe that there are, 
here and there, groups of stars which seem to be compressed 
together more densely than those in the neighboring parts ; 
forming bright patches or clusters. 

logues? Their object? What triple stars ? Ternary systems ? Quadruple stars, &c. ? 
24S. What said of the colors of the stars? What law of optics referred to? What illus- 
trations ? 249. What remarks respecting red and green suns, &c. ? Of insulated stars 
of a red color f 250. What said of clusters ? What specimen referred to ? Pleiades ? 



NEBULAS. 139 

The Pleiades are an instance of this kind, in which six or 
seven stars may be seen in near proximity, by the naked eye ; 
and even more if the eye be turned carelessly upon it ; for it is a 
remarkable fact that the center of the eye is far less sensible to 
feeble impressions of light, than the exterior portion of the retina. 
Rheita affirms that by the aid of a telescope he counted over 200 
stars in this small cluster. See Map VIII., Fig. 28. 

In the constellation called Coma Berenices there is another group 
more diffused, and consisting of much larger stars. In Cancer 
there is a nebulous cluster of very minute stars, called Prcesepe, 
or the Beehive, which is sufficiently luminous to be seen by the 
naked eye, in the absence of the moon, and which any ordinary 
spyglass will resolve into separate stars. In the sword-handle 
of Perseus, also, is another such spot, crowded with stars. It 
requires, however, rather a better telescope to resolve it into 
individual stars. See p. 65, and Map VIII., Fig. 39. 

Whatever be the nature of these clusters, it is certain that other laws of aggregation 
prevail in them, than those which have determined the scattering of stars over the gene- 
ral surface of the sky. Many of them, indeed, are of an exactly round figure, and con- 
vey the idea of a globular space filled full of stars, and constituting, in itself, a family or 
society apart, and subject only to its own internal laws. 

'' It would be a vain task," says the younger Herschel, " to attempt to count the stars 
in one of these globular clusters. They are not to be reckoned by hundreds ; for it would 
appear that many clusters of this description must contain, at least, ten or twenty thou- 
sand stars, compacted and wedged together in a round space, not more than a tenth part 
as large as that which is covered by the moon. 



NEBULAE. 

251. The lYebulce, so called from their dim, cloudy appearance, 
form another class of objects which furnish matter for curious 
speculation and conjecture respecting the formation and struc- 
ture of the sidereal heavens. When examined with a telescope 
of moderate powers, the greater part of the nebulae are dis- 
tinctly perceived to be composed of little stars, imperceptible to 
the naked eye, because, on account of their apparent proximity, 
the rays of light proceeding from each are blended together, in 
such a manner as to produce only a confused luminous appear- 
ance. 

In other nebulas, however, no individual stars can be perceived, even through the best 
telescopes; and the nebulae exhibit only the appearance of a self-luminous phosphores- 
cent patch of gaseous vapor, though it is possible that even in this case, the appearance 
maybe owing to a congeries of stars so minute, or so distant, as not to afford, singly, 
sufficient light to make an impression on the eye. 

Remarks upon their nature and the laws that govern them? Remarks of Herschel? 
251. What are nebulae, and why so called ? How appear through telescopes? Are they 
all resolvable into stars ? 



140 ASTRONOMY. 

252. One of the most remarkable nebulaB is in the sword- 
handle of Orion. It is formed of little flocky masses, like wisps 
of cloud, which seem to adhere to many small stars at its out- 
skirts. It is not very unlike the mottling of the sun's disc, but 
of a coarser grain, and with darker intervals. These wisps of 
light, however, present no appearance of being composed of 
small stars ; but in the intervals between them, we fancy that 
we see stars, or that, could we strain our sight a little more, we 
should see them. These intervals may be compared to openings 
in the firmament, through which, as through a window, we seem 
to get a glimpse of other heavens, and brighter regions, beyond. 
See page 45, and Map VIII., Fig. 32. 

253. Another very remarkable nebula is that in the girdle .of 
Andromeda, which, on account of its being visible. to the naked 
eye, has been known since the earliest ages of astronomy. It is 
often mistaken for a comet, by those unacquainted with the 
heavens. See page 20, and Map Till., Fig. 22. 

Marius, who noticed it in 1612, describes its appearance as that of a candle shining 
through horn; and the resemblance is certainly very striking. Its form is a long oval, 
increasing, by insensible gradations of brightness, from the circumference to a central 
point, which, though very much brighter than the rest, is not a star, but only a nebula in 
a high state of condensation. It occupies an area comparatively large — equal to that 
of the moon in quadrature. This nebula may be considered as a type, on a large scale, 
of a very numerous class of nebulaB, of a round or oval figure, increasing more or less in 
density toward the center. 

254. Annular nebula are those in the form of a ring, but are 
among the rarest objects in the heavens. The most conspicuous 
of this class is to be found exactly half-way between the stars 
Beta and Gamma Lyrae, and may be seen with a telescope of , 
moderate power. It is small, and particularly well defined ; 
appearing like a flat oval ring. The central opening is not 
entirely dark, but is filled with a faint, hazy light, uniformly 
spread over it, like a fine gauze stretched over a hoop. 

255. Planetary nebulce are very extraordinary objects. They 
have, as their name imports, the appearance of planets, with 
round or slightly oval discs, somewhat mottled, but approaching, 
in some instances, to the vividness of actual planets. Some of 
them, upon the supposition that they are equally distant from us 
with the stars, must be of enormous magnitude. That one, for 
instance, which is situated in the left hand of Aquarius, must 

252. What remarkable nebula mentioned? Describe it? Point out on the map. 
253. What other? How long known, and why ? Show on the map. How described by 
Marius? Its form and extent? How considered? 254. What are Annular Nebnlo: * 
are they common? What specimen referred to? 255. Planetary nebulae? Their 
character and magnitude ? Specimen ? Stellar nebulae ? General remarks respecting 



VIA LACTEA. 141 

have a volume vast enough, upon the lowest computation, to fill 
the whole orbit of Herschel ! 

In some instances a nebula presents the appearance of a faint, 
luminous atmosphere, of a circular form, and of large extent, 
surrounding a central star of considerable brilliancy. These are 
denominated Stellar Nebula. 

The nebulae furnish an inexhaustible field of speculation and conjecture. That by far 
the larger number of them consists of stars, there can be little doubt; and in the inter- 
minable range of system upon system, and firmament upon firmament, which we thus 
catch a glimpse of, the imagination is bewildered and lost. Sir William Herschel con- 
jectured that the nebulas might form the material out of which nature elaborated new 
suns and systems, or replenished the wasted light of older ones. But the little we know 
of the physical constitution of these sidereal masses, is altogether insufficient to warrant 
6uch a conclusion. (For a Spiral Nebula recently discovered by Lord Rosse, see Map IX., 
Fig. 68.) 



CHAPTER XIV. 

VIA LACTEA (the milky- way). 

" Throughout the Galaxy's extended line, 
Unnumber'd orbs in gay confusion shine : 
Where every star that gilds the gloom of night 
With the faint tremblings of a distant light, 
Perhaps illumes some system of its own, 
With the strong influence of a radiant sun." — Mrs. Carter. 

256. The Via Lactea, or Milky-Way, is that luminous zone 
or pathway of singular whiteness, varying from 4° to 20° in 
width, which passes quite around the heavens. The Greeks 
called it Galaxy, on account of its color and appearance : the 
Latins, for the same reason, called it Via Lactea, which, in our 
tongue, is Milky-Way. 

Of all the objects which the heavens exhibit to our view, this fills the mind with the 
most indescribable grandeur and amazement. When we consider what unnumbered 
millions of mighty suns compose this stupendous girdle, whose distance is so vast that 
the strongest telescope can hardly separate their mingled twilight into distinct specks, 
and that the most contiguous of any two of them may be as far asunder as our sun is 
from them, we fall as far short of adequate language to express our ideas of such immen- 
sity, as we do of instruments to measure its boundaries. 

25 Y. It is one of the achievements of astronomy that has* 
resolved the Milky- Way into an infinite number of small stars, 
whose confused and feeble luster occasions that peculiar white- 
ness which we see in a clear evening, when the moon is absent. 
It is also a recent and well-accredited doctrine of astronomy, 



the Nebulae? Sir Wm. Herschel's conjecture? 256. What is the Via Lactea? .Its 
Greek name? What said of its magnificence and grandeur? 257. What said of the 
achievements of astronomy? Its doctrine respecting the structure of the universe? 
Of the sun, and its relation to the fixed stars ? 



142 ASTRONOMY. 

that all the stars in the universe are arranged into clusters, or 
groups, which are called Nebula or Starry Systems, each of 
which consists of myriads of stars. 

The fixed star which we call our Sun, belongs, it is said, to that extensive nebula, the 
Milky- Way ; and although apparently at such an inmeasurable distance from its fellows, 
is, doubtless, as near to any one of them, as they are to one another. 

258. Of the number and economy of the stars which compose 
this group, we have very little exact knowledge. Dr. Herschel 
informs us that, with his best glasses, he saw and counted 588 
stars in a single spot, without moving his telescope ; and as the 
gradual motion of the earth carried these out of view and intro- 
duced others successively in their places, while he kept his tele- 
scope steadily fixed to one point, " there passed over his field 
of vision, in the space of one quarter of an hour, no lest than 
one hundred and sixteen thousand stars, and at another time, in 
forty-one minutes, no less than two hundred an,d fifty-eight thou- 
sandP 

In all parts of the Milky- Way he found the stars unequally dispersed, and appearing 
to arrange themselves into separate clusters. In the small space for example, between 
Beta and Sad'r, in Cygni, the stars seem to be clustering in two divisions ; each division 
containing upwards of one hundred and sixty-five thousand stars. At other observations, 
when examining a section of the Milky- Way, not apparently more than a yard in breadth, 
and six in length, he discovered fifty thousand stars, large enough to be distinctly 
counted ; and he suspected twice as many more, which, for want of sufficient light in his 
telescope, he saw only now and then. 

259. It appears from numerous observations, that various 
changes are taking place among the nebulas — that several nebu- 
las are formed by the disolution of larger ones, and that many 
nebulas of this kind are at present detaching themselves from 
the Milky-Way. In that part of it which is in the body of 
Scorpio, there is a large opening, about 4° broad, almost desti 
tute of stars. These changes seem to indicate that mighty 
movements and vast operations are continually going on in the 
distant regions of the universe, upon a scale of magnitude and 
grandeur which baffles the human understanding. 

More than two thousand five hundred nebulae have already been observed ; and, if 
each of them contains as many stars as the Milky- Way, several hundreds of millions of 
stars must exist, even within that portion of the heavens which lies open to our obser- 
vation. 

" what a confluence of ethereal fires. 
From urns unnumber'd down the steep of heaven 
Streams to a point, and centers on my sight." 

260. Although the Milky-Way is more or less visible at all 
seasons of the year, yet it is seen to the best advantage during 

258. Number and economy of the stars ? Dr. Herschel's statements ? What number 
passed the field of his instrument in a quarter of an hour ? In forty-one minutes ? In 
space apparently only a yard in breadth? 259. What changes observed in the nebu- 
las? What do they indicate? Number of nebulae? Estimated number of stars? 
260. When is the Via Lactea seen to the best advantage? Direction when Lyra is on the 



ORIGIN OF THE CONSTELLATIONS. 143 

the months of July, August, September, and October. When 
Lyra is on, or near the meridian, it may be seen stretching 
obliquely over the heavens from northeast to southwest, gradu- 
ally moving over the firmament in common with other constel- 
lations. (For views of our cluster, see Map IX., Figs. 69, 70, 71.) 

Its form, breadth and appearance are various, indifferent parts of its course. In some 
places it is dense and luminous; in others, it is scattered and faint. Its breadth is often 
not more than five degrees ; though sometimes it is ten or fifteen degrees, and even 
twenty. In some places it assumes a double path, but for the most part it is single. 

It may be traced in the heavens, beginning near the head of Cepheus, about 80° from 
the north pole, through the constellations Cassiopeia, Perseus, Auriga, and part of Orion 
and the feet of Gemini, where it crosses the Zodiac ; thence over the equinoctial into 
the southern hemisphere, through Monoceros, and the middle of the ship Argo, where it 
is most luminous, Charles' Oak, the Cross, the feet of the Centaur, and the Altar. Here 
it is divided into two branches, as it passes over the Zodiac again into the northern hem- 
isphere. One branch runs through the tail of Scorpio, the bow of Sagittarius, the shield 
of Sobieski, the feet of Antinous, Aquila, Delphinus, the Arrow and the Swan. The other 
branch passes through the upper part of the tail of Scorpio, the side of Serpentarius, 
Taurus Poniatowskii, the Goose and the neck of the Swan, where it again unites with the 
other branch, and passes on to the head of Cepheus, the place of its beginning. 

Some of the pagan philosophers maintained that the Milky- Way was formerly the sun's 
path, and that its present luminous appearance is the track which its scattered beams 
left visible in the heavens. 

The ancient poets, and even philosophers, speak of the Galaxy, or Milky-Way, as the 
path which their deities used in the heavens, and which led directly to the throne of 
Jupiter. Thus, Ovid, in his Metamorphoses, Book i. : — 

M A Way there is in heaven's extended plain, 
Which, when the skies are clear, is seen below, 
And mortals, by the name of Milky, know; 
The groundwork is of stars, through which the road 
Lies open to the Thunderer's abode." 

Milton alludes to this in the following lines : — 

" A broad and ample road, whose dust is gold, 
And pavement, stars, as stars to thee appear, 
Seen in the Galaxy, that Milky- Way, 
Which nightly as a circling zone, thou seest 
Powdered with stars." 



CHAPTER XY. 

ORIGIN" OF THE CONSTELLATION'S. 

261. The science of astronomy was cultivated by the imme- 
diate descendants of Adam. Josephtjs informs us that the sons 
of Seth employed themselves in the study of astronomy ; and 
that they wrote their observations upon two pillars, one of brick 

meridian? Its form, breadth, &c? How traced in the heavens? Notion of the Pagar 
philosophers ? Of the poets ? What citations ? 261. How early was astronomy cultivated ? 



144 ASTRONOMY. 

and the other of stone,* in order to preserve them against the 
destruction which Adam had foretold should come upon the earth. 

He also relates, that Abraham argued the unity and power of God, from the orderly 
course of things both at sea and land, in their times and seasons, and from his observa- 
tions upon the motions and influences of the sun, moon and stars ; and that he read lec- 
tures in astronomy and arithmetic to the Egyptians, of which they understood nothing 
till Abraham brought these sciences from Chaldea to Egypt ; from whence they passed to 
the Greeks. 

262. Berostjs also observes that Abraham was a great and just 
man, and famous for his celestial observation ; the making of 
which was thought to be so necessary to the human welfare, that 
he assigns it as the principal reason of the Almighty's prolong- 
ing the life of man. 

This ancient historian tells us, in his account of the longevity of the antediluvians, 
that Providence found it necessary to prolong man's days, in order to promote the study 
and advancement of virtue, and the improvement of geometry and astronomy, which 
required, at least, six hundred years for making and perfecting observations.t 

263. When Alexander took Babylon, Calisthenes found that 
the most ancient observations existing on record in that city, 
were made by the Chaldeans about 1903 years before that period, 
which carries us back to the time of the dispersion of mankind 
by the confusion of tongues. It was 1500 years after this that 
the Babylonians sent to Hezekiah, to inquire about the shadow's 
going back on the dial of Ahaz. 

It is, therefore, very probable that the Chaldeans and Egyptians were the original 
inventors of astronomy ; but at what period of the world they marked out the heavens 
into constellations, remains in uncertainty. La Place fixes the date thirteen or fourteen 
hundred years before the Christian era, since it was about this period that Eudoxus con- 
structed the first celestial sphere upon which the constellations were delineated. Sir 
Isaac Newton was of opinion, that all the old constellations related to the Argonautic 
expedition, and that they were invented to commemorate the heroes and events of that 
memorable enterprise. It should be remarked, however, that while none of the ancient 
constellations refer to transactions of a later date, yet we have various accounts of them 
of a much higher antiquity than that event. 

264. Some of the most learned antiquarians of Europe have 
searched every page of heathen mythology, and ransacked all 
the legends of poetry and fable for the purpose of rescuing this 
subject from that impermeable mist which rests upon it, and 
they have only been able to assure us, in general terms, that 
they are Chaldean or Egyptian hieroglyphics, intended to per- 
petuate, by means of an imperishable record, the memory of the 
times in which their inventors lived, their religion and manners, 

* Josephus affirms, that "he saw himself that of stone to remain in Syria in his own 
time." 
t Vince's Complete System of Astronomy, Vol. ii. p. 244. 



What proof? What said of Abraham? 262. What further proof? What reason 
assigned for the longevity of the antediluvians ? 263. What discovery by Calisthenes ? 
What conclusion from tlm discovery? La Place's date of the origin of the constella 
tions? Sir Isaac Newton's opinion? Remark? 264. What researches, and what 
results? 



ORIGIN OF THE CONSTELLATIONS. 145 

their achievements in the arts, and whatever in their history was 
most worthy of being commemorated. There was, at least, a 
moral grandeur in this idea ; for an event thus registered, a 
custom thus canonized, or thus enrolled among the stars, must 
needs survive all other traditions of men, and stand forth in per- 
petual characters to the end of time. 

265. In arranging the constellations of the Zodiac, for instance, 
it would be natural for them, we may imagine, to represent 
those stars which rose with the sun in the spring of the year, by 
such animals as the shepherds held in the greatest esteem at that 
season ; accordingly, we find Aries, Taurus, and Gemini, as the 
symbols of March, April, and May. 

266. When the sun enters the sign Cancer, at the summer 
solstice, he discontinues his progress towards the north pole, and 
begins to return towards the south pole. This retrograde mo- 
tion was fitly represented by a Crab, which is said to go back- 
ward. The sun enters this sign about the 22d of June. 

The heat whidvusually follows in the next month was repre- 
sented by the Lion ; an animal remarkable for its fierceness, 
and which at this season was frequently impelled by thirst to 
leave the sandy desert, and make its appearance on the banks 
of the Nile. 

267. The sun entered the sixth sign about the time of harvest, 
which season was therefore represented by a Virgin, or female 
reaper, with an ear of corn in her hand. 

At the autumnal equinox, when the sun enters Libra, the 
days and nights are equal all over the world, and seem to 
observe an equilibrium or balance. The sign was therefore 
represented under the symbol of a pair of Scales. 

268. Autumn, which produces fruit in great abundance, brings 
with it a variety of diseases, and on this account was represented 
by that venomous animal, the Scorpion, which, as he recedes, 
wounds with a sting in his tail. The fall of the leaf, was the 
season for hunting, and the stars which mark the sun's path at 
this time were represented by a huntsman, or archer, with his 
arrows and weapons of destruction. 

The Goat, which delights in climbing and ascending some 
mountain or precipice, is the emblem of the winter solstice, when 
the sun begins to ascend from the southern tropic, and gradually 
to increase in height for the ensuing half year. 



265. Origin of Aries, Taurus, and Gemini ? 266. Of Cancer and Leo ? 267. Of 
Virgo and Libra ? 263. Of Scorpio and Capricorn ? 



146 ASTRONOMY. 

269. Aquarius, or the Water- Bearer, is represented by the 
figure of a man pouring out water from an urn, an emblem of 
the dreary and uncomfortable season of winter. 

The last of the zodiacal constellations was Pisces, or a couple 
of fishes, tied back to back, representing the fishing season. 
The severity of winter is over ; the flocks do not afford suste- 
nance, but the seas and rivers are open and abound with fish. 

" Thus monstrous forms, o'er heaven's nocturnal arch, 
Seen by the sage, in pomp celestial march ; 
See Aries there his glittering bow unfold, 
And raging Taurus toss his horns of gold ; 
With bended bow the sullen Archer lowers, 
And there Aquarius comes with all his showers; 
Lions and Centaurs, G-orgons, Hydras rise, 
And gods and heroes blaze along the skies." 

Whatever may have led to the adoption of these rude names at first, they are now 
retained to avoid confusion. 

The early Greeks, however, displaced many of the Chaldean constellations, and sub- 
stituted such images in their place as had a more special reference to their own history. 
The Romans also pursued the same course with regard to their history ; and hence the 
contradictory accounts that have descended to later times. 

270. Some, moreover, with a desire to divest the science of 
the stars of its pagan jargon and profanity, have been induced 
to alter both the names and figures of the constellations. In 
doing this, they have committed the opposite fault ; that of 
blending them with things sacred. 

The " venerable Bede," for example, instead of the profane 
names and figures of the twelve constellations of the Zodiac, 
substituted those of the twelve apostles. Julius Schillerius, fol- 
lowing his example, completed the reformation in 1627, by giv- 
ing Scripture names to all the constellations in the heavens. 

Weigelius, too, a celebrated professor of mathematics in the University of Jena, made 
a new order of constellations, by converting the firmament into a ccelum heraldiccm, in 
which he introduced the arms of all the princes of Europe. But astronomers, generally, 
never approved of these innovations ; and for ourselves, we had as lief the sages and 
heroes of antiquity should continue to enjoy their fianced honors in the sky, as to see 
their places supplied by the princes of Europe. 

211. The number of the old constellations, including those of 
the Zodiac, was only forty-eight. As men advanced in the 
knowledge of the stars, they discovered many, but chiefly in 
southern latitudes, which were noc embraced in the old constel- 
lations, and hence arose that mixture of ancient and modern 
names which we meet with in modern catalogues. 

272. Astronomers divide the heavens into three parts, called 
the Northern and Southern Hemispheres, and the Zodiac. In the 

269. Of Aquarius and Pisces? Course of the Greeks and Romans, in displacing con- 
stellations? 270. What other reform attempted? What particular instances cited? 
Bede ? Schillerius ? Weigelius ? How are these innovations regarded by astronomers ? 
271. Number of the old constellations? How others added? 272. How do astrono 



ORIGIN OF THE CONSTELLATIONS. 147 

northern hemisphere, astronomers usually reckon thirty-four con- 
stellations, in the Zodiao twelve, and in the southern hemisphere 
forty-seven ; making in all ninety-three. Besides these, there 
are a few of inferior note, recently formed, which are not con- 
sidered sufficiently important to be particularly described. 

273. About the year 1603, John Bayer, a native of Germany, 
invented the convenient system of denoting the stars in each 
constellation by the letters of the Greek alphabet, applying to 
the largest star the first letter of the alphabet. ; to the next 
largest the second letter, and so on to the last. Where there 
are more stars in the constellation than there are Greek letters, 
the remainder are denoted by the letters of the Roman alphabet, 
and sometimes by figures. 

By this system of notation, it is now as easy to refer to any particular star in the 
heavens, as to any particular house in a populous city, by its street and number. Before 
this practice was adopted, it was customary to denote the stars by referring them to 
their respective situations in the figure of the constellation to which they severally 
belonged, as the head, the arm, the foot, &c. 

It is hardly necessary to remark that these figures, which are all very curiously depicted 
upon artificial globes and maps, are purely a fanciful invention — answering many con- 
venient ends, however, for purposes of reference and classification, as they enable us to 
designate with facility any particular star, or. cluster of stars ; though these clusters 
very rarely, if ever, represent the real figures of the objects whose names they bear. 
And yet it is somewhat remarkable that the name of " Great Bear," for instance, should 
have been given to the very same constellation by a nation of American aborigines (the 
Iroquois), and by the most ancient Arabs of Asia, when there never had been any com- 
munication between them ! Among other nations, also, between whom there exists no 
evidence of any intercourse, we find the Zodiac divided into the same number of constel- 
lations, and these distinguished by nearly the same names, representing the twelve 
months, or seascns of the year. 

274. The constellations, or the uncouth figures by which they 
are represented, are a faithful picture of the ruder stages of 
civilization. They ascend to times of which no other record 
exists ; and are destined to remain when all others shall be lost. 
Fragments of history, curious dates and documents relating to 
chronology, geography and languages, are here preserved in 
imperishable characters. 

The adventures of the gods, and the inventions of men, the exploits of heroes, and 
the fancies of poets, are here spread out in the heavens, and perpetually celebrated before 
all nations. The Seven stars, and Orion, present themselves to us, as they appeared to 
Amos and Homer : as they appeared to Job, more than 3000 years ago, when the 
Almighty demanded of him — " Knowest thou the ordinances of heaven? Canst thou 
bind the sweet influences of the Pleiades, or loose the bands of Orion? Canst thou 
bring forth Mazzaroth in his season, or canst thou guide Arcturus with his sons?" 
Here, too, are consecrated the lyre of Orpheus and the ship of the Argonauts ; and, in 
the same firmament, glitter the Mariner's Compass and the Telescope of Herschel. 

mers divide the constellations? Number in each division? Total? What others? 
273. John Bayer's invention? Utility of it? How before it was adopted? What remark 
respecting the figures on maps and globes, and their use? What remarkable facts 
stated? 274. Historical use of the constellations? Illustrations? 



B.G. 



148 ASTRONOMY. 

CHAPTER XYI. 

NUMBER, DISTANCE AND ECONOMY OF THE STARS. 

215. The first conjecture in relation to the distance of the 
fixed stars is, that they are all placed at an equal distance from 
the observer, upon the visible surface of an immense concave 
vault, which rests upon the circular boundary of the world, and 
which we call the Firmament. We can, with the unassisted eye, 
form no estimate of their respective distances ; nor has the tele- 
scope yet enabled us to arrive at any exact results on this sub- 
ject, although it has revealed to us many millions of stars that 
are as far removed beyond those which are barely visible to the 
naked eye, as these are from us. 

Viewed through the telescope, the heavens become quite another spectacle — not only 
to the understanding but to the senses. New worlds burst upon the sight, and old ones 
expand to a thousand times their former dimensions. Several of those little stars which 
but feebly twinkle on the unassisted eye, become immense globes, with land and water, 
mountains and valleys, encompassed by atmospheres, enlightened by moons, and diver- 
sified by day and night, summer and winter. 

Beyond these are other suns, giving light and life to other systems, not a thousand, or 
two thousand merely, but multiplied without end, and ranged all around us, at immense 
distances from each other, attended by ten thousand times ten thousand worlds, all in 
rapid motion ; yet calm, regular and harmonious — all space seems to be illuminated, and 
every particle of light a world. 

276. It has been computed that one hundred millions of stars 
which cannot be discerned by the naked eye, are now visible 
through the telescope. And yet all this vast assemblage of suns 
and worlds may bear no greater proportion to what lies beyond 
the utmost boundaries of human vision, than a drop of water to 
the ocean ; and, if stricken out of being, would be no more 
missed, to an eye that could take in the universe, than the fall 
of a single leaf from the forest. 

We should therefore learn, says Dr. Chalmers, not to look on our earth as the universe 
of God, but as a single, insignificant atom of it; that it is only one of the many mansions 
which the Supreme Being has created for the accommodation of his worshipers ; and 
that he may now be at work in regions more distant than geometry ever measured, creat- 
ing worlds more manifold than numbers ever reckoned, displaying his goodness, and 
spreading over all the intimate visitations of his care. 

2T7. The immense distance at which the nearest stars are 
known to be placed, proves that they are bodies of a prodigious 
size, not inferior to our sun, and that they shine, not by reflected 
rays, but by their own native light. It is therefore concluded, 

275. What is the first conjecture as to the distance of the stars? Can we form no just 
estimate? What said of the heavens when seen through a telescope? 276. What 
computation as to the number of stars invisible to the naked eye, but visible through 
telescopes ? Is this probably the whole universe ? Remark of Chalmers ? 277. What 



NUMBER, DISTANCE, AND ECONOMY OF THE STARS. 149 

with good reason, that every fixed star is a sun, no less spacious 
than ours, surrounded by a retinue of planetary worlds, which 
revolve around it as a center, and derive from it light and heat, 
and the agreeable vicissitudes of day and night. 

These vast globes of light, then, could never have been designed merely to diversify 
the voids of infinite space, nor to shed a few glimmering rays on our far distant world, 
for the amusement of a few astronomers, who, but for the most powerful telescopes, had 
never seen the ten thousandth part of them. We may therefore rationally conclude, that 
wherever the All-wise Creator has exerted his creative power, there also he has placed 
intelligent beings to adore his goodness. 

278. The greatest possible ingenuity and pains have been 
taken by astronomers to determine, at least, the approximate 
distance of the nearest fixed stars. If they have hitherto been 
unable to arrive at any satisfactory result, they have, at least, 
established a limit beyond which the stars must necessarily be 
placed. If they have failed to calculate their true distances 
from the earth, it is because they have not the requisite data. 
The solution of the problem, if they had the data, would not be 
more difficult than to compute the relative distances of the 
planets — a thing which any schoolboy can do. 

In estimating so great a distance as the nearest fixed star, it is necessary that we 
employ the longest measure which astronomy can use. Accordingly, we take the whole 
diameter of the earth's orbit, which, in round numbers, is 190 millions of miles, and 
endeavor, by a simple process in mathematics, to ascertain how many measures of this 
length are contained in the mighty interval which separates us from the stars.' 

The method of doing this can be explained to the apprehension of the pupil, if he does 
not shrink from the illustration, through an idle fear that it is beyond his capacity. 

For example ; suppose that, with an instrument constructed for the purpose, we should 
this night take the precise bearing or angular direction from us of some star in the 
northern hemisphere, and note it down with the most perfect exactness, and, having 
waited just six months, when the earth shall have arrived at the opposite point of its 
orbit, 190 millions of*miles east of the place which we now occupy, we should then repeat 
our observation upon the same star, and see how much it had changed its position by 
our traveling so great a distance one side of it. Now, it is evident, that if it changes its 
apparent position at all, the quantity of the change will bear some proportion to the 
distance gone over; that is, the nearer the star, the greater the angle; and the more 
remote the star, the less the angle. It is to be observed, that the angle thus found, i3 
called the star's Annual Parallax. 

279. But it is found by the most eminent astronomers of the 
age, and the most perfect instruments ever made, that the paral- 
lax of the nearest stars does not exceed the four thousandth part 
of a degree, or a single second ; so that, if the whole great orbit 
of the earth were lighted up into a globe of fire 600 millions of 
miles in circumference, it would be seen by the nearest star only 
as a twinkling atom ; and to an observer placed at this distance, 

proof that the stars are large bodies? What conclusion, therefore? What other 
inference ? 278. What effort to determine the distances of the stars ? What results ? 
What necessary in estimating the distances of the stars ? What measure taken ? De- 
scribe the process of determining the distance of the stars by parallax. 279. What 
is the parallax of the stars found to be, and what follows as a consequence ? What, 



150 ASTRONOMY. 

our sun, with its whole retinue of planetary worlds, would occupy 
a space scarcely exceeding the thickness of a spider's web.* 

If the nearest of the fixed stars are placed at such inconceivable distances in the 
regions of space, with what line shall we measure the distance of those which are a thou- 
sand or a million of times as much farther from them, as these are from us? 

280. If the annual parallax of a star were accurately known, 
it would be easy to compute its distance by the following rule : 

As the sine of the star's parallax : 

Is to radius, or ninety degrees : : 

So is the earth's distance from the sun : 

To the star's distance from the sun. 
If we allow the annual parallax of the nearest star to be 1", 
the calculation will be, 

As 0.0000048481368=Nat. Sine of 1". 

Is to 1.0000000000000=Nat. Sine of 90°. 

So is 95,273,868. 867748554 = Earth's distance from the sun. 

To 19,651, 627, 683,449 = Star's distance from the sun. 

In this calculation we have supposed the earth to be placed at the mean distance of 
&4,047 of its own semi-diameters, or 95,273,S68.S6774S554 miles from the sun, which makes 
the star's distance a very little less than twenty billions of miles. Dr. Herschel says 
that Sirius cannot be nearer than 100,000 times the diameter of the earth's orbit, or 
19,007,788,800,000 of miles. 

Biot, who either takes the earth's distance greater than he lays it down in his Traite 
Elementaire <V ' Astronomie Physique, or has made an error in figures, makes the dis- 
tance 20,080,868,036,404. Dr. Brewster makes it 20,159,665,000,000 miles. A mean of 
these computations, is 20 billions ; that is, 20 millions of millions of miles to a parallax 
of 1". 

Astronomers are generally agreed in the opinion that the annual parallax of the stars 
is less than 1", and consequently that the nearest of them is placed at a much greater 
distance from us, than these calculations make it. It was, however, announced in 1832, 
that M. d'Assas, a French astronomer, had satisfactorily established the annual parallax 
of Keid (a small star 8° N. of Gamma Eridani), to be 2", that of Higel, in Orion, to be 
1".43, and that of Sirius to be 1".24. If these results could be relied on, Keid would be 
but 10 billions, Rigel but 14 billions, and Sirius 16 billions of miles from the earth. This 
latter distance is, however, so great that, if Sirius were to fall toward the earth at 
the rate of a million of miles a day, it would take it forty-three thousand, three hundred 
years to reach the earth ; or, if the Almighty were now to blot it out of the heavens, its 
brilliance would continue undiminished in our hemisphere for the space of three years 
to come. 

* A just idea of the import of this term, will impart a force and sublimity to an expres- 
sion of St. James, which no power of words could improve. It is said, chapter i. verse 
17, of Him from whom cometh down every good and perfect gift, that there is " ovk evi 
7rapa?iAay?j r] rpoTzrjs arrocniiacrjua." Literally, there is "neither parallax nor 
shadow of change :" As if the apostle had said — Peradventure, that in traveling millions 
and millions of miles through the regions of immensity, there may be a sensible parallax 
to some of the fixed stars ; yet, as to the Father of Lights, view him from whatever point 
of his empire we may, he is without parallax or shadow of change I 

then, of the more distant stars? 280. How deduce the distance of a star from its 
parallax, if known? Computation laid down? Dr. Herschel's remark? Biot's estimate? 
Dr. Brewster's? The mean of these three estimates ? Are astronomers agreed as to the 
parallax of the stars ? M. d'Assas' computations and results ? 



NUMBER, DISTANCE, AND ECONOMY OF THE STARS. 151 

281. The most brilliant stars, till recently, were supposed to 
be situated nearest the earth, but later observations prove that 
this opinion is not well founded, since some of the smaller stars 
appear to have not only a greater annual parallax, but an 
absolute motion in space, much greater than those of the bright- 
est class. 

282. It has been computed that the light of Sirius, although 
twenty thousand million times less than that of our sun, is never- 
theless three hundred and twenty-four times greater than that of 
a star of the 6th magnitude. If we suppose the two stars to 
be really of the same size, it is easy to show that the star of the 
sixth magnitude is fifty-seven and one-third times farther from us 
than Sirius is, because light diminishes as the square of the dis- 
tance of the luminous body increases. 

By the same reasoning it may be shown, that if Sirius were placed where the sun is, it 
would appear to us to be four times as large as the sun, and give four times as much light 
and heat. It is by no means unreasonable to suppose, that many of the fixed stars 
exceed a million of miles in diameter. 

283. We may pretty safely affirm, then, that stars of the 
sixth magnitude are not less than nine hundred millions of millions 
of miles distant from us ; or a million of times farther from us than 
the planet Saturn, which is scarcely visible to the naked eye. 
But the human mind in its present state can no more appreciate 
such distances than it can infinity ; for if our earth, which moves 
at more than the inconceivable velocity of a million and a half 
of miles a day, were to be hurried from its orbit, and to take the 
same rapid flight over this immense tract, it would not traverse 
it in sixteen hundred thousand years ; and every ray of light, 
although it moves at the rate of one hundred and ninety-three 
thousand miles in a single second of time, is more than one hun- 
dred and seventy years in coming from the star to us. 

But what is even this, compared with that measureless extent which the discoveries of 
the telescope indicate? According to Dr. Herschel, the light of some of the nebulas, just 
perceptible through his 40 feet telescope, must have been a million of ages in coming to 
the earth; and should any of them be now destroyed, they would continue to be percep- 
tible for a million of ages to come. 

Dr. Herschel informs us, that the glass which he used would separate stars at 497 times 
the distance of Sirius. 

284. It is one of the wonders of creation, that any phenomena 
of bodies at such an immense distance from us should be percep- 
tible by human sight ; but it is a part of the Divine Maker's 

2S1. Former supposed relative distance of the most brilliant stars ? Present opinion, 
and on what founded ? 282. What computation as to the light of Sirius ? What con- 
clusion as to the distance of other stars ? How, then, would he appear if as near as our 
sun? What conclusion as to the magnitude of the stars? 283. Distance of the sixth 
magnitude stars? How measured by the flight of the earth ? Of light? What further 
estimate by Dr. Herschel? 284. What remark respecting our knowledge of the stara 



152 ASTRONOMY. 

plan, that although they do not act physically upon us, yet they 
should so far be objects of our perception, as to expand our ideas 
of the vastness of the universe, and of the stupendous extent 
and operations of his omnipotence. 

" With these facts before us," says an eminent astronomer and divine, " it is most rea- 
sonable to conclude, that those expressions in the Mosaic history of Creation, which 
relate to the creation of the fixed stars, are not to be understood as referring to the time 
when they were brought into existence, as if they had been created about the same time 
with our earth ; but as simply declaring the fact, that, at whatever period in duration 
they were created, they derived their existence from God." 

285. "That the stars here mentioned" (Gen.i. 16), says a 
distinguished commentator, "were the planets of our system, 
and not the fixed stars, seems a just inference from the fact, that 
after mentioning them, Moses immediately subjoins, ' And 
Elohim set them in the firmament of the heaven to give light 
upon the earth, and to rule over the day and over the night ;' 
evidently alluding to Yenus and Jupiter, which are alternately 
our morning and evening stars, and which ' give light upon the 
earth,' far surpassing in brilliancy any of the fixed stars." 

However vast the universe now appears, however numerous the worlds which may 
exist within its boundless range, the language of Scripture, and Scripture alone, is suffi- 
ciently comprehensive and sublime to express all the emotions which naturally arise in 
the mind when contemplating its structure. This shows not only the harmony which 
subsists between the discoveries of the Revelation and the discoveries of Science, but 
also forms, by itself, a strong presumptive evidence, that the records of the Bible are 
authentic and divine. 

286. We have hitherto described the stars as being immov- 
able and at rest ; but from a series of observations on double 
stars, Dr. Herschel found that a great many of them have 
changed their situations with regard to each other ; that some 
perform revolutions about others, at known and regular periods, 
and that the motion of some is direct, while that of others is 
retrograde ; and that many of them have dark spots upon their 
surface, and turn on their axes, like the sun. 

287. A remarkable change appears to be gradually taking 
place in the relative distances of the stars from each other in 
the constellation Hercules. The stars in this region appear to 
be spreading farther and farther apart, while those in the oppo- 
site point of the heavens seem to close nearer and nearer together, 
in the same manner as when walking through a forest, the trees 
toward which we advance appear to be constantly separating, 
while the distance between those which we leave behind is gra- 
dually contracting. 

by sight? How arc we to understand Moses as to the time of the creation of the stars? 
2S5. What meant by the " stars" mentioned Gen. i., 16 ? What proof? Remark respect- 
ing the Scriptures ? 286. How have the stars been described hitherto? What is the 
fact ? 287. What example cited ? What astonishing conclusion ? 



NUMBER, DISTANCE, AND ECONOMY OF THE STARS. 153 

From this appearance it is concluded, that the sun, with all its retinue of planetary 
worlds, is moving through the regions of the universe, toward some distant center, or 
around some wide circumference at the rate of near thirty thousand miles an hour ; and 
that it is therefore highly probable, if not absolutely certain, that we shall never occupy 
that portion of absohite space, through which we are at this moment passing, during 
all the succeeding ages of eternity. 

288. The direction of the Sun's motion is towards the constel- 
lation of Hercules ;* R. A. 259° ; Dec. 35°. This velocity 
in space is estimated at 8 miles per second, or 28,000 miles 
per hour. His period is about 18,200,000 years ; and the 
arc of his orbit, over which he has traveled since the creation 
of the world, amounts to only about 3 oVo^ P art or " ms orD it, or 
about 1 minutes — an arc so small, compared with the whole, as 
to be hardly distinguishable from a straight line. 

With this wonderful fact in view, we may no longer consider the sun as fixed and sta- 
tionary, but rather as a vast and luminous planet, sustaining the same relation to some 
central orb that the primary planets sustain to him, or that the secondaries sustain to 
their primaries. Nor is it necessary that the stupendous mechanism of nature should be 
restricted even to these sublime proportions. The sun's central body may also have its 
orbit, and its center of attraction and motion, and so on, till, as Dr. Dick observes, we 
come to the great center of all — to the throne of God ! 

Professor Madler, of Dorpat, in Russia, has recently announced as a discovery that 
the star Alcyone, one of the seven stars, is the center around which the sun and solar 
system are revolving. 

289. Dr. Dick, the author of the Christian Philosopher, 
endeavors to convey some idea of the boundless extent of the 
universe, by the following sublime illustration : — 

"Suppose that one of the highest order of intelligences is 
endowed with a power of rapid motion superior to that of light, 
and with a corresponding* degree of intellectual energy ; that he 
has been flying without intermission, from one province of crea- 
tion to another, for six thousand years, and will continue the 
same rapid course for a thousand million years to come, it is 
highly probable, if not absolutely certain, that, at the end of this 
vast tour, he would have advanced no farther than the ' sub- 
urbs of creation/ — and that all the magnificent systems of mate- 
rial and intellectual beings he had surveyed, during his rapid 
flight, and for such a length of ages, bear no more proportion to 
the whole empire of Omnipotence, than the smallest grain of 
sand does to all the particles of matter contained in ten thousand 
worlds." 

Were a seraph, in prosecuting the tour of creation in the manner now stated, ever to 
arrive at a limit beyond which no farther displays of the Divinity could be perceived, the 
thought would overwhelm his faculties with unutterable emotions ; he would feel that he 
had now, in some measure, comprehended all the plans and operations of Omnipotence, 
and that no farther manifestation of the Divine glory remained to be explored. But we 
may rest assured that this can never happen in the case of any created intelligence. 

2SS. The direction and velocity of the sun ? Period? Arc of orbit passed over since 
creation? How, then, should we consider the sun? View of the universe ? Discovery 
of Professor Madler ? 289. Dr. Dick's illustrations ? 



154 ASTRONOMY. 

290. There is, moreover, an argument derivable from the 
laws of the physical world, that seems to strengthen, I had 
almost said, to confirm, this idea of the Infinity of the material 
universe. It is this — If the number of stars be finite, and 
occupy only a part of space, the outward stars would be con- 
tinually attracted to those within, and in time would unite in 
one. But if the number be infinite, and they occupy an infinite 
space, all parts would be nearly in equilibrio, and consequently 
each fixed star, being equally attracted in every direction, would 
keep its place. 

No wonder, then, that the Psalmist was so affected with the idea of the immensity of 
the universe, that he seems almost afraid lest he should be overlooked amidst the immen- 
sity of beings that must needs be under the superintendence of God ; nor that any finite 
mortal should exclaim, when contemplating the heavens — " What is man, that THOU 
art mindful of him !" 



CHAPTER XVII. 

FALLING, OR SHOOTING STARS. 

291. The phenomenon of shooting stars, as it is called, is com- 
mon to all parts of the earth ; but is most frequently seen in 
tropical regions. The unerring aim, the startling velocity, and 
vivid brightness with which they seem to dart athwart the sky, 
and as suddenly expire, excite our admiration ; and we often 
ask, " What can they be V* 

But frequent as they are, this interesting phenomenon is not 
well understood. Some imagine that they are occasioned by 
electricity, and others, that they are nothing but luminous gas. 
Others again have supposed, that some of them are luminous 
"bodies which accompany the earth in its revolution around the 
sun, and that their return to certain places might be calculated 
with as much certainty and exactness as that of any of the 
comets. 

292. Dr. Burney, of Gosport, kept a record of all that he 
observed in the course of several years. The number which he 
noticed in 1819 was 121, and in 1820 he saw 131. Professor 

290. What argument supposed to favor the idea of a boundless universe? Allusion to 
the Psalmist? 291. Where are shooting stars most common? Are they well under- 
stood ? What theories stated ? 292. Dr. Burney's record? Professor Green's opinion? 
Signior Baccaria's opinion, and his reasons for it? 



FALLING OR SHOOTING STARS. 155 

Green is confident that a much larger number are annually seen 
in the United States. 

Signior Baccaria supposed they were occasioned by electricity, 
and thinks this opinion is confirmed by the following observa- 
tions. About an hour after sunset, he and some friends, that 
were with him, observed a falling star directing its course directly 
toward them, and apparently growing larger and larger, but just 
before it reached them it disappeared. On vanishing, their 
faces, hands, and clothes, with the earth and all the neighboring 
objects, became suddenly illuminated with a diffused and lambent 
light. It was attended with no noise. During their surprise at 
this appearance, a servant informed them that he had seen a 
light shine suddenly in the garden, and especially upon the 
streams which he was throwing to water it. 

The SigDior also observed a quantity of electric matter collect about his kite, which 
had very much the appearance of a falling star. Sometimes he saw a kind of halo 
accompanying the kite, as it changed its place, leaving some glimmering of light in the 
place it had quitted. 

293.. Shooting stars have been supposed by those meteorolo- 
gists who refer them to electricity or luminous gas, to prognos- 
ticate changes in the weather, such as rain, wind, &c. ; and there 
is, perhaps, some truth in this opinion. The duration of the 
brilliant track which they leave behind them, in their motion 
through the air, will probably be found to be longer or shorter, 
according as watery vapor abounds in the atmosphere. 

The notion that this phenomenon betokens high winds, is of great antiquity. Virgil, 
in the first book of his Georgics, expresses the same idea : — 

" Ssepe etiam Stellas vento impendente videbis 
Prsecipites ccelolabi; noctisque per umbram 
Flammarum longos a tergo albescere tractus." 
•' And oft, before tempestuous winds arise, 
The seeming stars fall headlong from the skies, 
And shooting through the darkness, gild the night 
With sweeping glories and long trails of light." 

294. The number of shooting stars observed in a single night, 
though variable, is commonly very small. There are, however, 
several instances on record of their falling in " showers " — when 
every star in the firmament seems loosened from its sphere, and 
moving in lawless flight from one end of the heavens to the 
other. 

As early as the year 472, in the month of November, a phe- 
nomenon of this kind took place near Constantinople. As Theo- 

293. What are they supposed by some to prognosticate? What other ancient notion? 
Poetic quotation? 294. What said of the number of shooting stars? What instances 
of " meteoric showers " cited ? 

7* 



156 ASTRONOMY, 

phanes relates, " the sky appeared to be on fire," with the corus- 
cations of the flying meteors. 

A shower of stars exactly similar took place in Canada, between the 3d and 4th of 
July, 1814, and another at Montreal, in November, 1819. In all these cases, a residuum, 
or Mack dust, was deposited upon the surface of the waters, and upon the roofs of build- 
ings, and other objects. In the year 1810, " inflamed substances," it is said, fell into, 
and around lake Van, in Armenia, which stained the water of a blood color, and cleft 
the earth in various places. On the 5th of September, 1819, a like phenomenon was seen 
in Moravia. History furnishes many more instances of meteoric showers, depositing a 
red dust in some places, so plentiful as to admit of chemical analysis. 

295. The commissioner (Mr. Andrew Ellicott), who was sent 
out by our government to fix the boundary between the Spanish 
possessions in North America and the United States, witnessed 
a very extraordinary flight of shooting stars, which filled the 
whole atmosphere from Cape Florida to the West India Islands. 
This grand phenomenon took place the 12th of November, IT 9 9, 
and is thus described : — " I was called up," says Mr. Ellicott, 
" about 3 o'clock in the morning, to see the shooting stars, as 
they are called. The phenomenon was grand and awful. The 
whole heavens appeared as if illuminated with sky-rockets, 
which disappeared only by the light of the sun, after daybreak. 
The meteors, which at any one instant of time appeared as 
numerous as the stars, flew in all possible directions except from 
the earth, toward which they all inclined more or less, and some 
of them descended perpendicularly over the vessel we were in, so 
that I was in constant expectation of their falling on us." 

Mr. Ellicott further states that his thermometer, which had been at 80° Pahr. for the four 
days preceding, fell to 56° about 4 o'clock, A. M., and that nearly at the same time, the 
wind changed from the south to the northwest, from whence it blew with great violence 
for three days without intermission. 

These same appearances were observed the same night at Santa Fe de Bogota, Cu- 
maaa, Quito, and Peru, in South America ; and as far north as Labrador and Greenland, 
extending to Weimar in Germany, being thus visible over an extent on the globe of 64° 
of latitude, and 94" of longitude. 

The celebrated Humboldt, accompanied by M. Bompland, 
then in S. America, thus speaks of the phenomenon : — " Toward 
the morning of the 13th of November, 1799, we witnessed a 
most extraordinary scene of shooting meteors. Thousands of 
bolides, and falling stars succeeded each other during four hours. 
Their direction was very regular from north to south. From 
the beginning of the phenomenon there was not a space in the 
firmament, equal in extent to three diameters of the moon, 
which was not filled every instant with bolides or falling stars. 
AH the meteors left luminous traces, or phosphorescent bands 
behind them, which lasted seven or eight seconds." 

•295. What phenomenon described by Mr. Ellicott ? When and where? Effect on his 
thermometer? Where els,e observed, and by whom? 



FALLING OR SHOOTING STARS 157 

This phenomenon was witnessed by the Capuchin missionary at San Fernando de 
Afiura, a village situated in lat. 7° 53' 12", amidst the savannahs of the province of 
Varinas ; by the Franciscan monks stationed near the cataracts of the Oronoco, and at 
Marca, on the banks of the Rio Negro, lat. 2° 40", long. 70° 21', and in the west of Braz.il, 
as far as the equator itself; and also at the city of Porto Cabello, lat. 10° 6' 52% in French 
Guiana, Popayan, Quito, and Peru. It is somewhat surprising that the same appearances, 
observed in places so widely separated, amid the vast and lonely deserts of South 
America, should have been seen, the same night, in the United States, in Labrador, in 
Greenland, and at Itterstadt, near Weimar, in Germany! 

296. We are told that thirty years before, at the city of 
Quito, "there was seen in one part of the sky, above the volcano 
of Cayamburo, so great a number of falling stars, that the moun- 
taiu was thought to be in names. This singular sight lasted 
more than an hour. The people assembled in the plain of Exida, 
where a magnificent view presents itself of the highest summits 
of the Cordilleras. A procession was already on the point of 
setting out from the convent of St. Francis, when it was per- 
ceived that the blaze on the horizon was caused by fiery meteors, 
which ran along the sky in all directions, at the altitude of 12 
or 13 degrees." 

297. But the most sublime phenomenon of shooting stars, of 
which the world has furnished any record, was witnessed through- 
out the United States on the morning of the 13th of November, 
1833. The entire extent of this astonishing exhibition has not 
been precisely ascertained, but it covered no inconsiderable por- 
tion of the earth's surface. It has been traced from the longi- 
tude of 61°, in the Atlantic ocean, to longitude 100° in Central 
Mexico, and from the Xorth American lakes to the West Indies. 
It was not seen, however, anywhere in Europe, nor in South 
America, nor in any part of the Pacific Ocean yet heard from. 

Everywhere, within the limits above mentioned, the first 
appearance was that of fireworks of the most imposing grandeur, 
covering the entire vault of heaven with myriads of fire-balls, 
resembling sky-rockets. Their coruscations were bright, gleam- 
ing and incessant, and they fell thick as the flakes in the early 
snows of December. (See cut on the next page.) 

To the splendors of this celestial exhibition, the most brilliant sky-rockets and fire- 
works of art bear less relation than the twinkling of the most tiny star to the broad 
glare of the sun. The whole heavens seemed in motion, and suggested to some the awful 
grandeur of the image employed in the apocalypse, upon the opening of the sixth seal, 
when " the stars of heaven fell unto the earth, even as a fig-tree casteth her untimely 
figs, when she is shaken of a mighty wind." 

298. One of the most remarkable circumstances attending 
this display was, that the meteors all seemed to emanate from 

296. What other similar phenomenon cited ? 297. What still more sublime spectacle? 
Its extent? Its appearance? 



158 



ASTRONOMY. 



one and the same point, a little southeast of the zenith. Follow- 
ing the arch of the sky, they ran along with immense velocity, 
describing, in some instances, an arc of 30° or 40° in a few 




METEORIC SHOWER OF NOVEMBER, 1833. 



seconds. On more attentive inspection it was seen, that the 
meteors exhibited three distinct varieties ; the first, consisting 
of phosphoric lines, apparently described by a point ; the second, 
of large fire-balls, that at intervals darted along the sky, leaving 
luminous trains, which occasionally remained in view for a num- 
ber of minutes, and, in some cases, for half an hour or more ; 
the third, of undefined luminous bodies, which remained nearly 
stationary in the heavens for a long time. 

Those of the first variety were the most numerous, and resembled a shower of fiery 
snow driven with inconceivable velocity to the north of west. The second kind appeared 
more like falling stars — a spectacle which was contemplated by the more unenlightened 
beholders with great amazement and terror. The trains which they left were commonly 
white, but sometimes were tinged with various prismatic colors, of great beauty. 

299. These fire-balls were occasionally of enormous size. Dr. 
Smith, of North Carolina, describes one which appeared larger 
than the full moon rising. " I was," says he, " startled by the 

298. What remarkable circumstance attended this phenomenon ? Variety of meteors ? 
299. What said of the fireballs seen? Of their size? 



FALLING OR SHOOTING STARS. 




A LARGE METEOR. 



splendid light in which the surrounding scene was exhibited, ren- 
dering even small objects quite visible." 

The same ball, or a similar one, 
seen at New Haven, passed off in a 
northwest direction, and exploded a 
little northward of the star Capella, 
leaving, just behind the place of 
explosion, a train of peculiar beauty. 
The line of direction was at first 
nearly straight; but it soon began to 
contract in length, to dilate in breadth, 
and to assume the figure of a serpent 
scrolling itself up, until it appeared 
like a luminous cloud of vapor, float- 
ing gracefully in the air, where it 
remained in full view for several 
minutes. 

If this body were at the distance of 
110 miles from the observer, it must 
have had 'a diameter of one mile ; if 
at the distance of 11 miles, its diame- 
ter was 528 feet ; and if only one mile 

off, it must have been 48 feet in diameter. These tonsiderations leave no doubt that 
many of the meteors were bodies of large size. 

300. Of the third variety of meteors, the following are remark- 
able examples : — At Poland, Ohio, a luminous body was dis- 
tinctly visible in the northeast for more than an hour. It was 
very brilliant, in the form of a pruning-hook, and apparently 
twenty feet long, and eighteen inches broad. It gradually 
settled toward the horizon, until it disappeared. 

At Niagara Falls, a large luminous body, shaped like a square table, was seen near 
the zenith, remaining for some time almost stationary, emitting large streams of light. 

301. The point from which the meteors seemed to emanate, 
was observed, by those who fixed its position among the stars, 
to be in constellation Leo ; and, according to their concurrent 
testimony, this radiant point was stationary among the stars, 
during the whole period of observation ; that is, it did not move 
along with the earth, in its diurnal revolution eastward, but 
accompanied the stars in their apparent progress westward. 

A remarkable change of weather, from warm to cold, accompanied the meteoric 
shower, or immediately followed it. In all parts of the United States, this change was 
remarkable for its suddenness and intensity. In many places, the day preceding had 
been unusually warm for the season, but, before the next morning, a severe frost ensued, 
unparalleled for the time of year. 

302. In attempting to explain these mysterious phenomena, it 
is argued, in the first place, that the meteors had. their origin 
beyond the limits of our atmosphere ; that they of course did not 
belong to this earth, but to the regions of space exterior to it. 



300. What other variety of meteors described? Where? 301. Point from which 
they seemed to emanate ? What change of weather followed ? 302. What fact asserted 
as to the distance from which those meteors came? Professor Olmsted's estimate of 
distance? 



160 ASTRONOMY. 

The reason on which the conclusion is founded is this : — All bodies near the earth, 
including the atmosphere itself, have a common motion with the earth around its axis 
from west to east; but the radiant point, that indicated the source from which the 
meteors emanated, followed the course of the stars from east to west ; therefore, it was 
independent of the earth's rotation, and consequently, at a great distance from it, and 
beyond the limits of the atmosphere. The height of the meteoric cloud, or radiant point, 
above the earth's surface, was, according to the mean average of Professor Olmsted's 
observations, not less than 223S miles. 

303. That the meteors were constituted of very light, combus- 
tible materials, seems to be evident, from their exhibiting the 
actual phenomena of combustion, they being consumed, or con- 
verted into smoke, with intense light ; and the extreme tenuity 
of the substance composing them is inferred from the fact that 
they were stopped by the resistance of the air. Had their quan- 
tity of matter been considerable, with so prodigious a velocity, 
they would have had sufficient momentum to dash them upon 
the earth ; where the most disastrous consequences might have 
followed. 

The momentum of even light bodies of such size, and in such numbers, traversing the 
atmosphere with such astonishing velocity, must have produced extensive derangements 
in the atmospheric equilibrium. Cold air from the upper regions would be brought down 
to the earth ; the portions of air incumbent over districts of country remote from each 
other, being mutually displaced, would exchange places, the air of the warm latitudes be 
transferred to colder, and that of cold latitudes to warmer regions. 

304. Various hypotheses have been proposed to account for this 
wonderful phenomena. The agent which most readily suggests 
itself in this, and in many other unexplained natural appearances, 
is electricity. But no known properties of electricity are adequate 
to account for the production of the meteors, for their motions, or 
for the trains which they, in many instances, left behind them. 
Others, again, have referred their proximate cause to ?nagnetism. 
and to phosphureted hydrogen ; both of which, however, seem to 
be utterly insufficient, so far as their properties are known, to 
account for so unusual a phenomenon. , 

305. Professor Olmsted, of Yale College, who has taken much 
pains to collect facts, and to establish a permanent theory for 
the periodical recurrence of such phenomena, came to the con- 
clusion, that — 

The meteors of November lZth, 1833, emanated from a nebulous 
body, which wa.s then pursuing its way along with the earth around 
the sun ; that this body continues to revolve around the, sun, in an 
elliptical orbit — but little inclined to the plane of the ecliptic, and 
having its aphelion near the orbit of the earth ; and finally, that 

803. Supposed composition of these meteors? Why? 304. Hypotheses for explain- 
ing phenomenon? Are they satisfactory? 805. Professor Olmsted's conclusion? 



FALLING OR SHOOTING STARS. 161 

the body has a period of nearly six months, and that its perihelion 
is a little below the orbit of Mercury.* 

This theory at least accommodates itself to the remarkable fact, that almost all the 
phenomena of this description, which are known to have happened, have occurred in the 
two opposite months of April and November. A similar exhibition of meteors to that of 
November, 1833, was observed on the same day of the week, April 20th, 1803, at Rich- 
mond, Virginia ; Stockbridge, Massachusetts ; and at Halifax, in British America. Another 
was witnessed in the autumn of 1818, in the North Sea, when, in the language of the 
observers, " all the surrounding atmosphere was enveloped in one expansive sea of fire, 
exhibiting the appearance of another Moscow, in flames." 

* After the first edition of this work went to press, the author was politely fur- 
nished, by Professor Olmsted, with the following communication. 

" I am happy to hear that you propose to stereotype your ' Geography of the Heavens.' 
it has done much, I believe, to diffuse a popular knowledge of astronomy, and I am pleased 
that your efforts are rewarded by an extended patronage. 

"Were I now to express my views on the subject (Meteoric Showers) in as condensed 
a form as possible, I should state them in some such terms as the following : The meteoric 
3howers which have occurred for several years past on or about the 13th of November, 
are characterized by four peculiarities, which distinguish them from ordinary shooting 
stars. First, they are far more numerous than common, and are larger and brighter. 
Secondly, they are in much greater proportion than usual, accompanied by luminous 
trains. Thirdly, they mostly appear to radiate from a common center ; that is, were 
their paths in the heavens traced backward, they would meet in the same part of the 
heavens : this point has for three years past, at least, been situated in the constellation 
Leo. Fourthly, the greatest display is everywhere at nearly the same time of night, 
namely, from three to four o'clock — a time about half-way from midnight to sunrise. The 
meteors are inferred to consist of combustible matter, because they are seen to take fire 
and burn in the atmosphere. They are known to be very light, because, although they 
fall toward the earth with immense velocity, few, if any, ever reach the earth, but are 
arrested by the air, like a wad fired from a piece of artillery. Some of them are inferred 
to be bodies of comparatively great size, amounting in diameter to several hundred feet, 
at least, because they are seen under so large an angle, while they are at a great distance 
from the spectator. Innumerable small bodies, thus consisting of extremely light, thin, 
combustible matter, existing together in space far beyond the limits of the atmosphere, 
are believed to compose a body of immense extent, which has been called ' the nebulous 
body.' Only the skirts or extreme portions of this are brought down to the earth, while 
the entire extent occupies many thousands, and perhaps several millions of miles. This 
nebulous body is inferred to have a revolution around the sun, as well as the earth, and 
to come very near to the latter about the 13th of November each year. This annual 
meeting every year, for several years in succession, could not take place unless the 
periodic time of the nebulous body is either nearly a year, or half a year. Various rea- 
sons have induced the belief that half a year is the true period ; but this point is con- 
sidered somewhat doubtful. The zodiacal light, a faint light that appears at different 
seasons of the year, either immediately preceding the morning or following the evening 
twilight, ascending from the sun in a triangular form, is, with some degree of probability, 
thought to be the nebular body itself, although the existence of such a body, revolving 
in the solar system, was inferred to be the cause of the meteoric showers, before any 
connection of it with the zodiacal light was even thought of." 

With what remarkable fact does his theory accord ? Substance of letter from Professor 
Olmsted? 



162 ASTRONOMY. 

306. Exactly one year previous to the great phenomenon of 
1833, namely, on the 12th of November, 1832, a similar meteoric 
display was seen near Mocha, on the Red Sea, by Capt. Ham- 
mond and crew of the ship Restitution. 

A gentleman in South Carolina thus describes the effect of the phenomenon of 1833, 
upon his ignorant blacks : " I was suddenly awakened by the most distressing cries that 
ever fell on my ears. Shrieks of horror, and cries of mercy, I could hear from most of 
the negroes of three plantations, amounting in all to about six or eight hundred. While 
earnestly listening for the cause, I heard a faint noise near the door calling my name ; 
I arose, and taking my sword, stood at the door. At this moment, I heard the same 
voice still beseeching me to rise, and saying, '0, my God, the world is on fire !' I then 
opened the door, and it is difficult to say which excited me most — the awfulness of the 
scene, or the distressed cries of the negroes ; upward of one hundred lay prostrate on the 
ground — some speechless, and some with the bitterest cries, but most with their hands 
raised, imploring God to save the world and them. The scene was truly awful ; for 
aever did rain fall much thicker, than the meteors fell toward the earth ; east, west, 
north, and south, it was the same !" 

306. What similar meteoric shower referred to ? Description of that of November 
1833, and its effects upon certain persons ? 



PART II. 
THE SOLAR SYSTEM 



CHAPTER I. 

GENERAL PHENOMENA OF THE SOLAR SYSTEM, 
HISTORY, &o. 

307. Our attention has hitherto been directed to those bodies 
which we see scattered everywhere throughout the whole celes- 
tial concave. These bodies, as has been shown, twinkle with a 
reddish and variable light, and appear to have always the same 
position with regard to each other. We know that their num- 
ber is very great, and that their distance from us is immeasur- 
able. 

We are also acquainted with their comparative brightness, and their situation. In a 
word, we have before us their few visible appearances, to which our knowledge of them 
is well-nigh limited ; almost all our reasonings in regard to them being founded on com- 
paratively few and uncertain analogies. Accordingly, our chief business thus far has 
been to detail their number, to describe their brightness and positions, and to give the 
names by which they have been designated. 

308. There now remain to be considered certain other celes- 
tial bodies, all of which, from their remarkable appearance and 
changes, and some of them from their intimate connection with 
the comfort, convenience, and even existence of man, must have 
always attracted especial observation, and been objects of the 
most intense contemplation and the deepest interest. Most of 
these bodies are situated within the limits of the Zodiac. The 
most important of them are, the Sun, so superior to all the 
heavenly bodies for its apparent magnitude, for the light and 
heat which it imparts, for the marked effects of its changes of 
position with regard to the Earth ; and the Moon, so conspicu- 
ous among the bodies which give light by night, and from her 

307. Subject of Part IT.? Of our investigations hitherto? How distinguished ? Then 
number, distance, &c. ? What has been our chief business thus far? 308. What now 
remains to be considered? How situated? Which the most important of them? 



1 64 ASTRONOMY. 

soft and silvery brightness, so pleasing to behold ; remarkable 
not only for changes of position, but for the varied phases or 
appearances which she presents, as she waxes from her crescent 
form through all her different stages of increase to a full orb, 
and wanes back again to her former diminished figure. 

309. The partial or total obscuration of these two bodies, 
which sometimes occurs, darkness taking place even at mid-day, 
and the face of night, before lighted up by the Moon's beams, 
being suddenly shaded by their absence, have always been among 
the most striking astronomical phenomena, and so powerful in 
their influence upon the beholders, as to fill them with perplexity 
and fear. 

310. If we observe these two bodies, we shall find that, 
besides their apparent diurnal motion, across the heavens, they 
exhibit other phenomena, which must be the effect of motion. 
The Sun during one part of the year will be seen to rise every 
day farther and farther toward the north, to continue longer and 
longer above the horizon, to be more and more elevated at mid- 
day, until he arrives at a certain limit ; and then, during the 
other part, the order is entirely reversed. 

311. Again ; if the Sun's motions be attentively observed, he 
will be found to have another motion, opposite to his apparent 
diurnal motion from east to west. This may be perceived dis- 
tinctly, if we notice, on any clear evening, any bright star which 
is first visible after sunset, near the place where he sunk below 
the horizon. The following evening, the star will not be visible 
on account of the approach of the Sun, and all the stars on the 
east of it will be successively eclipsed by his rays, until he shall 
have made a complete apparent revolution in the heavens. 
These are the most obvious phenomena exhibited by these two 
bodies. 

312. The Moon sometimes is not seen at all ; and then, when 
she first becomes visible, appears in the west, not far from the 
setting Sun, with a slender crescent form ; every night she 
appears at a greater distance from the setting Sun, increasing in 
size, until at length she is found in the east, just as the Sun is 
sinking below the horizon in the west. 

313. There are also situated within the limits of the Zodiac 
certain other bodies, which, at first view and on a superficial 
examination, are scarcely distinguishable from the fixed stars. 

309. What said of their obscuration ? 310. Of their motions ? 311. Has the Sun 
an apparent eastward motion? 312. What said of the Moon's motions and phases? 
813. What other bodies and their motions? What called, and why ? 



PHENOMENA OF THE SOLAR SYSTEM. 165 

But, observed more attentively, they will be seen to shine with 
a milder and steadier light, and, besides being carried round 
with the stars, in the apparent revolution of the great celestial 
concave, they will seem to change their places in the concave 
itself. Sometimes they are stationary ; sometimes they appear 
to be moving from west to east, and sometimes to be going back 
again from east to west ; being seen at sunset sometimes in the 
east, and sometimes in the west, and always apparently changing 
their position with regard to the earth, each other, and the 
other heavenly bodies. From their wandering, as it were, in 
this manner through the heavens, they were called by the Greeks 
irXavTjTCU, planets, which signifies wanderers. 

314. There also sometimes appear in the heavens, bodies of a 
very extraordinary aspect, which continue visible for a considera- 
ble period, and then disappear from our view ; and nothing more 
is seen of them, it may be, for years, when they again present 
themselves, and take their place among the bodies of the celes- 
tial sphere. They are distinguished from the planets by a dull 
and cloudy appearance, and by a train of light. As they 
approach the sun, however, their faint and nebulous light becomes 
more and more brilliant, and their train increases in length 
until they arrive at their nearest point of approximation, when 
they shine with their greatest brilliancy. As they recede from 
the Sun, they gradually lose their splendor, resume their faint 
and nebulous appearance, and their train diminishes, until they 
entirely disappear. They have no well-defined figure ; they 
seem to move in every possible direction, and are found in every 
part of the heavens. From their train they were called by the 
Greeks tco[i7]Tai, comets, which signifies bearded, or having 
long hair. 

The causes of these various phenomena must have early constituted a very natural 
subject of inquiry. Accordingly, we shall find, if we examine the history of the science, 
that in very early times there were many speculations upon this subject, and that differ- 
' ent theories were adopted to account for these celestial appearances. 

315. The Egyptians, Chaldeans, Indians, and Chinese, early 
possessed many astronomical facts, many observations of impor- 
tant phenomena, and many rules and methods of astronomical 
calculation ; and it has been supposed, that they had the ruins 
of a great system of astronomical science, which in the earliest 
ages of the world had been carried to a great degree of perfec- 
tion, and that while the principles and explanations of the phe- 

314. Any other bodies described? How distinguished? What called, and why ? Is it 
probable that these phenomena were early observed ? 315. What said of the Egyptians, 
Chaldeans, &c? Of the Chinese in particular? Of the Indians and Chaldeans? 



166 ASTRONOMY. 

nomena were lost, the isolated, unconnected facts, rules of calcu- 
lation, and phenomena themselves, remained. 

Thus, the Chinese, who, it is generally agreed, possess the oldest authentic observa- 
tions on record, have recorded in their annals, a conjunction of five planets at the same 
time, which happened 2461 years before Christ, or 100 years before the flood. By mathe- 
matical calculation, it is ascertained that this conjunction really occurred at that time. 
The first observation of a solar eclipse of which the world has any knowledge, was made 
by the Chinese, 212S years before Christ, or 220 years after the deluge. It seems, also, 
that the Chinese understood the method of calculating eclipses; for, it is said, that the 
emperor was so irritated against the great officers of state for neglecting to predict the 
eclipse, that he caused them to be put to death. The Chinese have, from time imme- 
morial, considered Solar Eclipses and conjunctions of the planets, as prognostics of 
importance to the Empire, and they have been predicted as a matter of state policy. 

The astronomical epoch of the Chinese, according to Bailly, commenced with Fohi, 
their first emperor, who flourished 2952 years before the Christian era, or about 350 
years before the deluge. If it be asked how the knowledge of this antediluvian astrono- 
my was preserved and transmitted, it is said that the columns on which it was registered 
have survived the deluge, and that those of Egypt are only copies which have become 
originals, now that the others have been forgotten. The Indians, also, profess to have 
many celestial observations of a very early date. The Chaldeans have been justly cele- 
brated in all ages for their astronomical observations. When Alexander took Babylon, 
his preceptor, Callisthenes, found a series of Chaldean observations, made in that city, 
and extending back, with little interruption, through a period of 1903 years preceding 
that event. This would carry us back to at least 2234 years before the birth of Christ, 
or to about the time of the dispersion of mankind by the confusion of tongues. 

316. The Greeks, in all probability, derived many notions 
in regard to this science, and many facts and observations, from 
Egypt, the great fountain of ancient learning and wisdom, and 
many were the speculations and hypotheses of their philosophers. 
The first of the Greek philosophers who taught Astronomy was 
Thales, of Miletus. He flourished about 640 years before the 
Christian era. Then followed Anaximander, Anaximenes, 
Anaxagoras, Pythagoras, Plato. 

Some of the doctrines maintained by these philosophers were, that the Earth was 
round, that it had two motions, a diurnal motion on its axis, and an annual motion 
around the Sun, that the Sun was a globe of fire, that the Moon received her light from 
the Sun, that she was habitable, contained mountains, seas, &c. ; that her eclipses were 
caused by the Earth's shadow, that the planets were not designed merely to adorn our 
heavens, that they were worlds of themselves, and that the fixed stars were centers of 
distant systems. Some of them, however, maintained that the Earth was flat, and others 
that, though round, it was at rest in the center of the universe. 

317. When that distinguished school of philosophy was estab- 
lished at Alexandria, in Egypt, by the munificence of the sove- 
reigns to whom that portion of Alexander's empire had fallen, 
astronomy recived a new impulse. It was now, in the second 
century after Christ, that the first complete system or treatise 
of astronomy of which we have any knowledge, was formed. 
All before had been unconnected and incomplete. Ptolemy, 
with the opinions of all antiquity, and of all the philosophers 

316. Of the Greeks? Who first taught astronomy among them? Date? Who next? 
State some of their doctrines? 317. What record of this science? What of Ptolemy 
and his works ? 



PHENOMENA OF THE SOLAR SYSTEM. 167 

who had preceded him, spread out before him, composed a work 
in thirteen books, called the MeyaXr] Zvvra^tg, or Great System. 

318. Rejecting the doctrine of Pythagoras, who taught that 
the Sun was the center of the universe, and that the Earth had 
a diurnal motion on its axis and an annual motion around the 
Sun, as contrary to the evidence of the senses, Ptolemy endea- 
vored to account for the celestial phenomena, by supposing the 
Earth to be the center of the universe, and all the heavenly 
bodies to revolve around it. 

He seems to have entertained an idea, in regard to the supposition, that the Earth 
revolved on its axis, similar to one which some entertain even at the present day. " If," 
ssays he, "there were any motion of the Earth common to it and all other heavenly 
bodies, it would certainly precede them all by the excess of its mass being so great; and 
animals and a certain portion of heavy bodies would be left behind, riding upon the air, 
and the earth itself would very soon be completely carried out of the heavens." 

319. In explaining the celestial phenomena, however, upon 
his hypothesis, he met with a difficulty in the apparently station- 
ary attitude and retrograde motions which he saw the planets 
sometimes have. To explain this, however, he supposed the 
planets to revolve in small circles, which he called epicycles, 
which were, at the same time, carried around the Earth in 
larger circles, which he called deferents, or carrying circles. 

In following out his theory, and applying it to the explanation of different phenomena, 
it became necessary to add new epicycles, and to have recourse to other expedients, until 
the system became unwieldy, cumbrous, and complicated. This theory, although astro- 
nomical observations continued to be made, and some distinguished astronomers appeared 
from time to time, was the prevailing theory until the middle of the 15th century. It was 
not, however, always received with implicit confidence ; nor were its difficulties always 
entirely unappreciated. 

Alphonso X., king of Castile, who flourished in the 13th century, when contemplating 
the doctrine of the epicycles, exclaimed, " Were the universe thus constructed, if the 
Deity had called me to his councils at the creation of the world, I could have given him 
good advice." He did not, however, mean any impiety or irreverence, except what was 
directed against the system of Ptolemy. 

320. About the middle of the 15th century, Copernicus, a 
native of Thorn in Prussia, conceiving a passionate attachment 
to the study of astronomy, quitted the profession of medicine, 
and devoted himself with the most intense ardor to the study of 
this science. " His mind," it is said, " had long been imbued 
with the idea that simplicity and harmony should characterize 
the arrangements of the planetary system. In the complication 
and disorder which he saw reigned in the hypothesis of Ptolemy, 
he perceived insuperable objections to its being considered as a 
representation of nature." 

31S. His system of astronomy? What singular idea and reasoning? 319. What 
difficulty did he meet with, and how explain it ? What further difficulty ? How long 
did this theory prevail? What anecdote of the King of Castile? 320. What dis- 
tinguished student of astronomy now arose ? His impressions in regard to the Ptolemaic 
theory ? His own earlier convictions? What other theories did he study? 



168 ASTRONOMY. 



In the opinions of the Egyptian sages, in those of Pythagoras, Philolaus, Aristarchus, 
and Nicetas, he recognized his own earliest conviction that the Earth was not the center 
of the universe. His attention was much occupied with the speculation of Martinug 
Capella, who placed the Sun between Mars and the Moon, and made Mercury and Venug 
revolve round him as a center, and with the system of Appollonius Pergceus who made 
all the planets revolve around the Sun, while the Sun and Moon were carried around the 
Earth in the center of the universe. 

321. The examination, however, of various hypotheses, by 
Copernicus, gradually expelled the difficulties with which the 
subject was beset, and after the labor of more than thirty years, 
he was permitted to see the true system of the universe. The 
Sun he considered as immovable, in the center of the system, 
while the Earth revolved around him, between the orbits of 
Yenus and Mars, and produced by its rotation about its axis all 
the diurnal phenomena of the celestial sphere. The other planets 
he considered as revolting about the Sun, in orbits exterior to 
that of the Earth. ( See the Relative Distances of the Planets 1 
Orbits, Map I. of the Atlas.) 

Thus, the stations and retrogradations of the planets were the necessary consequence 
of their own motions, combined with that of the Earth about the Sun. He said that " by 
long observation, he discovered that, if the motions of the planets be compared with 
that of the Earth, and be estimated according to the times in which they perform their 
revolutions, not only their several appearances would follow from this hypothesis, but 
that it would so connect the older of the planets, their orbits, magnitudes, and distances, 
and even the apparent motion of the fixed stars, that it would be impossible to remove 
one of these bodies out of its place without disordering the rest, and even the whole of 
the universe also." 

322. Soon after the death of Copernicus, arose Tycho Brahe, 
born at Knudstorp, in Norway, in 1546. Such was the distinc- 
tion which he had attained as an astronomer, that when, dissa- 
tisfied with his residence in Denmark, he had resolved to remove, 
the King of Denmark, learning his intentions, detained him in 
the kingdom, by presenting him with the canonry of Rothschild, 
with an income of 2,000 crowns per annum. He added to this 
sum a pension of 1,000 crowns, gave him the island of Huen, 
and established for him an observatory at an expense of about 
200,000 crowns. Here Tycho continued, for twenty-one years, 
to enrich astronomy with his observations. 

His observations upon the Moon were important, and upon the planets numerous and 
precise, and have formed the data of the present generalizations in astronomy. He, 
however, rejected the system of Copernicus ; considering the Earth as immovable in the 
center of the system, while the Sun, with all the planets and comets revolving around 
him, performed his revolution around the earth, and, in the course of twenty-four hours, 
the stars also revolved about the central body. This theory was not so simple as that of 
Copernicus, and involved the absurdity of making the Sun, planets, &c, revolve around 
a body comparatively insignificant. 

321. How was Copernicus led to discover the true system of astronomy? What is that 
system? Does it account for the stations and retrogradations of the planets? 322. 
What distinguished astronomer next arose? What said of his detention in Denmark? 
His observations ? His theory 



PHENOMENA OF THE SOLAR SYSTEM. 16$ 

323. Near the close of the 15th century, arose two men, who 
wrought most important changes in the science ; Kepler and 
Galileo, the former a German, the latter an Italian. Previous 
to Kepler, all investigations proceeded upon the supposition that 
the planets moved in circular orbits which had been a source of 
much error. This supposition Kepler showed to be false. He 
discovered that their orbits were ellipses. The orbits of their 
secondaries or moons he also found to be the same curve. He 
next determined the dimensions of the orbits of the planets, and 
found to what their velocities in their motions through their 
orbits, and the times of their revolutions, were proportioned; all 
truths of the greatest importance to the science. 

324. While Kepler was making these discoveries of facts, very 
essential for the explanation of many phenomena, Galileo was 
discovering wonders in the heavens never before seen by the eye 
of man. Having improved the telescope, and applied it to the 
heavens, he observed mountains and valleys upon the surface of 
our Moon ; satellites or secondaries were discovered revolving 
about Jupiter ; and Venus, as Copernicus had predicted, was 
seen exhibiting all the different phases of the Moon, waxing and 
waning as she does, through various forms. 

Many minute stars, not visible to the naked eye, were described in the Milky-Way ; and 
the largest fixed stars, instead of being magnified, appeared to be small brilliant points, 
an incontrovertible argument in favor of their immense distance from us. All his dis- 
coveries served to confirm the Copernican theory, and to show the absurdity of the 
hypothesis of Ptolemy. 

325. Although the general arrangement and motions of the 
planetary bodies, together with the figure of their orbits, had 
been thus determined, the force of power which carries them 
around in their orbits, was as yet unknown. The discovery of 
this was reserved for the illustrious Newton, though even his 
discovery was in some respects anticipated by Copernicus, 
Kepler and Hooke. By reflecting on the nature of gravity— 
that power which causes bodies to descend toward the center of 
the earth — since it does not sensibly diminish at the greatest 
distance from the center of the earth to which we can attain, 
being as powerful on the loftiest mountains as it is in the deepest 
caverns, he was led to imagine that it might extend to the 
Moon, and that it might be the power which kept her in her 
orbit, and caused her to revolve around the Earth. He was 
next led to suppose that perhaps the same power carried the 

823. What two noted astronomers next arose ? What did Kepler discover ? 324. 
Galileo and his discoveries? What theory did they serve to establish? 325 What 
great discovery next made, and by whom? How led to it? Successive step3? 



170 ASTRONOMY. 

primary planets around the Sun. By a series of calculations, 
he was enabled at length to establish the fact, that the same 
force which determines the fall of an apple to the Earth, carries 
the moons in their orbits around the planets, and the planets 
and comets in their orbits around the Sun. 

To recapitulate briefly : The system (not hypothesis, for much of it has been established 
by mathematical demonstration) by which we are now enabled to explain with a beauti- 
ful simplicity the different phenomena of the Sun, planets, moons, and comets, is, that 
the Sun is the central body in the system: that the planets and comets move round him 
in elliptical orbits, whose planes are more or less inclined to each other, with velocities 
bearing to each other a certain ascertained relation, and in times related to their dis- 
tances ; that the moons, or secondaries, revolve in like manner about their primaries, 
and at the same time accompany them in their motion around the Sun ; all meanwhile 
revolving on axes of their own ; and that these revolutions in their orbits are produced 
by the mysterious power of attraction. The particular mode in which this system is 
applied to the explanation of the different phenomena, will be exhibited as we proceed to 
consider, one by one, the several bodies above mentioned. 

326. These bodies, thus arranged and thus revolving, consti- 
tute what is termed the Solar System. The planets have been 
divided into two classes, primaries and secondaries. The latter 
are also termed moons, and sometimes satellites. The primaries 
are those that revolve about the Sun, as a center. The seconda- 
ries are those which revolve about the primaries. There have 
been discovered to this date (1854), thirty-live primary planets, 
viz.: Mercury, Yenus, the Earth, Mars, Flora, Clio, Yesta, Iris, 
Metis, Eunomia, Psyche, Thetis, Melpomene, Fortuna, Massiiia, 
Lutetia, Calliope, Thalia, Hebe, Parthenope, Irene, Egeria, 
Astrsea, Juno, Ceres, Pallas, Hygeia, Jupiter, Saturn, Uranus, 
Neptune, and four other Asteroids, whose names and places have 
not yet been determined. Mercury is the nearest to the Sun, 
und the others follow in the order in which they are named. The 
seventeen small planets from Flora to Hygeia, inclusive, were dis- 
covered by means of the telescope, and, because they are very 
small, compared with the others, are called Asteroids. Neptune, 
also, is a telescopic planet, though much larger than any of the 
Asteroids. 

There have been discovered twenty secondaries. Of these, 
the Earth has one, Jupiter four, Saturn eight, Herschel six, and 
Neptune one All these, except our Moon, as well as the Aste- 
roids and Neptune, are invisible to the naked eye. 

Map I. of the Atlas, " exhibits a plan of the Solar System," comprising the relative 
magnitudes of the Sun and Planets ; their comparative distances from the Sun, and from 
each other; the position of their orbits, with respect to each other; the Earth and the 
Sun ; together with many other particulars which are explained on the map. There, the 

Describe the Copernican theory? 326. What do the bodies mentioned constitute? 
How are the planets divided? Describe each? What number of primaries ? Name 
them in order from the Sun ? Which are the Asteroids ? Which telescopic ? How many 
secondary planets? How distributed? Are they visible to the naked eye ? What said 



THE SUN HIS DISTANCE, MAGNITUDE, ETC. 171 

first and most prominent object which claims attention, is the representation of the 
Sun's circumference, with its deep radiations, bounding the upper margin of the map. 
It is apparent, however, that this segment is hardly one-sixth of the whole circumference 
of which it is a part. Were the map sufficiently large to admit the entire orb of the Sun, 
even upon so diminutive a scale as there represented, we should then see the Sun and 
Planets in their just proportions — the diameter of the former being 112 times the diameter 
of the Earth. 

It was intended, originally, to represent the Earth upon a scale of one inch in diameter 
and the other bodies in that proportion ; but it was found that it would increase the map 
to four times its size ; and hence it became necessary to assume a scale of half an inch 
for the Earth's diameter, which makes that of the Sun 56 inches, and the other bodies, as 
represented upon the map. 

The relative position of the Planets' orbits is also represented, on a scale as large as 
the sheet would permit. Their relative distances from the Sun as a center, and from each 
other, are there shown correctly. But had we wished to enlarge the dimensions of these 
orbits, so that they would exactly correspond with the scale to which we have drawn the- 
planets, the map must have been nearly two miles in length. " Hence," says Sir John 
Herschel, " the idea that we can convey correct notions on this subject, by drawing circles 
on paper, is out of the question." 

To illustrate this — Let us suppose ourselves standing on an extended plane, or field of 
ice, and that a globe 4 feet S inches in diameter is placed in the center of the plane, to 
represent the Sun. Having cut out of the map the dark circles representing the planets, 
we may proceed to arrange them in their respective orbits about the Sun, as follows : 

First, we should take Mercury, about the size of a smill currant, and place it on the 
circumference of a circle 194 feet from the Sun; this circle would represent the orbit of 
Mercury, in the proper ratio of its magnitude. Next, we should take Venus, about the 
size of a rather small cherry, and place it on a circle 362 feet from the Sun, to represent 
the orbit of Venus, Then would come the Earth, about the size of a cherry, revolving in 
an orbit 500 feet from the Sun. After the Earth we should place Mars, about the size of 
a cranberry, on a circle 762 feet from the Sun. Neglecting the Asteroids, some of which 
would not be larger than a pin's head, we should place Jupiter, hardly equal to a mode- 
rate-sized melon, on a circle at the distance of half a mile (2601 feet) from the Sun; 
Saturn, somewhat less, on a circle nearly a mile (4768 feet) from the Sun ; Herschel, about 
the size of a peach, on the circumference of a circle nearly 2 miles (9591 feet) from the 
San ; and last of all Neptune, a little larger than Herschel, and on a circle of nearly 3 
miles (15,366 feet) from the Sun. 

To imitate the motions of the planets in the above-mentioned orbits, Mercury must 
describe its own diameter in 41 seconds ; Venus, in 4 minutes 14 seconds ; the Earth, in 
7 minutes; Mars, in 4 minutes 48 seconds; Jupiter, in 2 hours 56 minutes; Saturn, in 
3 hours 13 minutes ; Herschel, in 12 hours 16 minutes ; and Neptune, in 23 hours 25 min. 

Many other interesting subjects are embraced in Map I. ; but they are either explained 
on the map, or in the following chapters, to which they respectively relate. 



CHAPTER II. 

THE SUN— HIS DISTANCE, MAGNITUDE, &c. 

32*1. The Sun is a vast globe, in the center of the solar sys- 
tem, dispensing light and heat to all the planets, and governing 
all their motions. It is the great parent of vegetable life, giv- 
ing warmth to the seasons, and color to the landscape. Its rays 
are the cause of various phenomena on the surface of the earth 
and in the atmosphere. By their agency, all winds are pro- 
of Map I. ? Its scale ? Remark of Dr. Herschel? What illustrations of the Solar System 
does he furnish ? 327. Subject of Chapter H.? Describe the Sun? 

B.G. 8 



172 ASTRONOMY. 

duced, and the waters of the sea are made to circulate in vapor 
through the air, and irrigate the land, producing springs and rivers. 

328. The Sun is by far the largest of the heavenly bodies 
whose dimensions have been definitely ascertained. Its diameter 
is about 886,000 miles. Consequently, it contains a volume 
of matter equal to fourteen hundred thousand globes of the size 
of the Earth. Of a body so vast in its dimensions, the human 
mind, with all its efforts, can form no adequate conception. 

the sun and the moon's orbit. Were the Sun a hollow sphere, perforated with 

a thousand openings to admit the twinkling c-f 
the luminous atmosphere around it — and were a 
globe as large as the Earth placed at its center, 
with a satellite as large as our Moon, and at the 
same distance from it as she is from the earth, 
there would be present to the eye of a spectator 
on the interior globe, a universe as splendid as 
that which now appears to the uninstructed eye 
— a universe as large and extensive as the 
whole creation was conceived to be in the 
infancy of astronomy. 

The mean distance of the Moon from the 
Earth is 240,000 miles, consequently the average 
diameter of her orbit is 480,000 miles ; and yet, 
' were the Sun to take the place of the Earth, he 
would fill the whole orbit of the Moon, and 
extend 200,000 miles beyond it in every direc- 
tion I To pass from side to side through his 
center, at railroad speed (30 miles an hour), 
would require nearly three and a half years , 
and to traverse his vast circumference nearly eleven years. 

Here let the student refer to Map I., where the Relative Magnitudes of the Sun and 
Planets are exhibited. Let him compare the segment of the Sun's circumference, as 
there represented, with the entire circumference of the Earth. They are both drawn upon 
the same scale. The segment of the Sun's circumference, since it is almost a straight 
line, must be a very small part of what the whole circumference would be, were it repre- 
sented entire. Let the student understand this diagram, and he will be in some measure 
able to conceive how like a mere point the Earth is, compared with the Sun, and to form 
in his mind some image of the vast magnitude of the latter. 

329. The next thing which fills the mind with wonder, is the 
distance at which so great a body must be placed, to occupy, 
apparently, so small a space in the firmament. The Sun's mean 
distance from the Earth is twelve thousand times the Earth's 
diameter, or a little more than 95,000,000 of miles. We may 
derive some faint conception of such a distance, by considering 
that the swiftest steamboats, which ply our waters at the rate 
of 200 miles a day, would not traverse it in thirteen hundred 
years ; and, that a cannon ball, flying night and day, at the 
rate of 16 miles a minute, would not reach it in eleven years. 

330. The Sun, when viewed through a telescope, presents the 
appearance of an enormous globe of fire, frequently in a state of 
violent agitation or ebullition ; dark spots of irregular form, 

828. His magnitude ? Diameter ? Compared with the Earth ? What illustration given? 
What reference to the Map? 329. Distance of the Sun? What illustration given? 
830. How does the Sun appear through a telescope ? Describe these spots ? 




THE SUN HIS DISTANCE, MAGNITUDE, ETC. 



173 




rarely visible to the naked eye, frequently pass over his disc, 
from east to west, in the period of nearly fourteen days. 

These spots are usually surrounded by a spots on thb sck. 

penumbra, or less deeply shaded border, 
and that, by a margin of light more bril- 
liant that that of the Sun. A spot when 
first seen on the eastern edge of the Sun, 
appears like a line which progressively ex- 
tends in breadth, and increases its appa- 
rent velocity, till it reaches the middle, 
when it begins to contract, and to move 
less rapidly, till it ultimately disappears at 
the western edge. In some rare instances, 
the same spots re-appear on the east side, 
and are permanent for two or three revo- 
lutions. But, as a general thing, the spots 
on the Sun are neither permanent nor uni- 
form. Sometimes several small ones unite 
into a large one ; and, again, a large one 
separates into numerous small ones. Some 
continue several days, weeks, and even 
months, together; while others appear and 
disappear, in the course of a few hours. 
Those spots that are formed gradually, are, 
for the most part, as gradually dissolved ; 
whilst those that are suddenly formed, generally vanish as quickly. 

331. It is the general opinion, that spots on the Sun were 
first discovered by Galileo, in the beginning of the year 1611 ; 
though Scheiner, Harriot, and Fabricius, observed them about 
the same time. During a period of 18 years from this time, the 
Sun was never found entirely clear of spots, excepting a few 
days in December, 1624 : at other times, there were frequently 
seen twenty or thirty at a time, and in 1625, upwards of fifty 
were seen at once. From 1650 to 1610, scarcely any spots were 
to be seen ; and, from 1676 to 1684, the orb of the Sun pre- 
sented an unspotted disc. Since the beginning of the eighteenth 
century, scarcely a year has passed, in which spots have not 
been visible, and frequently in great numbers. In 1199, Dr. 
Herschel observed one nearly 30,000 miles in breadth. 

A single second of angular measure, on the Sun's disc, as seen from the Earth, corre- 
sponds to 462 miles ; and a circle of this diameter (containing therefore nearly 220,000 
square miles) is the least space which can be distinctly discerned on the Sun as a -visible 
area, even by the most powerful glasses. Spots have been observed, however, whose 
linear diameter has been more than 44,000 miles ; and, if some records are to be trusted, 
of even still greater extent. 

Dr. Dick, in a letter to the author, says : " I have for many years examined the solar 
spots with considerable minuteness, and have several times seen spots which were not 
less than the one twenty-fifth part of the Sun's diameter, which would make them about 
22,192 miles in diameter, yet they were visible neither to the naked eye, nor through an 
opera glass magnifying about three times. And, therefore, if any spots have been visi- 
ble to the naked eye — which we must believe, unless we refuse respectable testimony — 
they could not have been much less than 50,000 miles in diameter." 

331. Who first saw them ? When ? How was it for the next IS years ? How in 1625 ? 
From 1650 to 1670? From 1676 to 1684? How since the beginning of the eighteenth 
century? Dr. Herschel's measurements? Dr. Dick's remarks and conclusion? 



174 



ASTRONOMY. 



332. The apparent direction of these spots over the Sun's disc 
is continually varying. Sometimes they seem to move across it 
in straight lines, at others in curve lines. Sometimes the spots 
seem to move upward, as they cross from east to west, while at 
other times they incline downward, while the curve lines are 
sometimes convex towards one pole of the Sun, and sometimes 
towards the other. 

333. All these phenomena are owing to the fact that the axis 
of the Sun is inclined to the ecliptic, so that viewing him from 
different points in the Earth's orbit, the apparent direction of 
the spots must necessarily vary. The following diagrams may 
serve to illustrate : 



VARIOUS DIRECTIONS OF THE SOLAR SPOTS. 
B 




March. 



June. 



December 



September. 

Let E F represent the plane of the ecliptic. In March, the spots describe a curve, 
which is convex to the south, as shown at A. In June, they cross the Sun's disc in nearly- 
straight lines, but incline upward. In September, they curve again, though in the oppo- 
site direction ; and in December, pass over in straight lines, inclining downward. The 
figures B and D show the inclination of the Sun's axis. 

The following diagram will servo still further to illustrate the 
cause of the change of direction of the solar spots. 



SOLAR SPOTS OBSERVED FROM DIFFERENT POINTS. 



DM. 




Let the student imagine himself Btationed upon the earth at A, in March, looking upon 
the sun in the center, whose north or upper pole is now inclined toward him. The spots 
will then curve downward. Three months afterward— viz., in June— the earth will be 



332. In what general direction do these spots move ? What variations ? 
is the cause of these varying phenomena? 



833. What 



THE SUN HIS DISTANCE, MAGNITUDE, ETC. 175 

at B ; when the sun's axis will incline to the left, and the spots seem to pass upward to 
the right. In three months longer, the observer will be at C, when the north pole of the 
sun will incline from him, and the spots seem to curve upward; and in three months 
longer, he will be at D, when the axis of the sun will incline to the right, and the spots 
seem to incline downward. 

334. From the regularity with which these spots revolve, it 
is concluded, with good reason, that they adhere to the surface 
of the Sun and revolve with it. They are all found within 30° 
of his equator, or within a zone 60 in width. 

335. The apparent revolution of a spot, from any particular 
point of the Sun's disc, to the same point again, is accomplished 
in 27 days, 7 hours, 26 minutes, and 24 seconds ; but during 
that time, the spot has, in fact, gone through one revolution, 
together with an arc, equal to that described by the Earth in 
her orbit in the same time ; which reducest he time of the Sun's 
actual rotation on his axis, to 25 days, 9 hours, and 36 minutes. 

Let S represent the sun, and A sidebeal and synodic revolutions of the sun. 
the earth in her orbit. When she 
is at A, a spot is seen upon the / 

disc of the sun at B. The sun re- E 
volves in the direction of the ar- * ,*$SV^- 

rows, and in 25 days 10 hours the ^p'"-— $lDrD r . 

spot comes round to B again, or } """'^SSo i n 

opposite the star E. This is a. side- •« '''-'Ms 

real revolution. • F ""*" 

During these 25 days 8 hours, 
the earth has passed on in her 1 * _- «jltf \.„ 

orbit some 25°, or nearly, to C, ; ««vH0^ C -^ *"***" 

which will require nearly two days • .$£ 

for the spot at B, to get directly ^Exta"""****"* 

toward the earth, as shown at D. ^gfC 

This last is a synodic revolution. \ 

It consists of one complete revolu- ' 

tion of the sun upon his axis, and 
about 27° over. 

336. The part of the Sun's disc not occupied by spots, is far 
from being uniformly bright. Its ground is finely mottled with 
an appearance of minute dark dots, or pores, which, attentively 
watched for several days in succession, are found to be in a con- 
stant state of change. 

What the physical organization of the Sun may be, is a ques- 
tion which astronomy, in its present state, cannot solve. It 
seems, however, to be surrounded by an ocean of inexhaustible 
flame, with dark spots of enormous size, now and then floating 
upon its surface. From these phenomena, Sir W. Herschel sup- 
posed the Sun to be a solid, dark body, surrounded by a vast 

334. Are these spots supposed to adhere to the body of the Sun ? On what part of the 
Sun are they found ? 335. What is their time of apparent revolution ? The actual 
time? How arrived at? 336. What said of the part of the Sun about his poles? Of 
his physical organization? What does it seem to be? How did Sir W. Herschel 
regard it? 




176 ASTRONOMY. 

atmosphere, almost always filled with luminous clouds, occasion- 
ally opening and disclosing the dark mass within. 

33 1. The speculations of Laplace were different. He im- 
agined the solar orb to be a mass of fire, and the violent effer- 
vescences and explosions seen on its surface, to be occasioned by 
the eruption of elastic fluids, formed in its interior, and the spots 
to be enormous caverns, like the craters of our volcanoes. 
Others have conjectured that these spots are the tops of solar 
mountains, which are sometimes left uncovered by the luminous 
fluid in which they are immersed. 

338. Among all the conflicting theories that have been 
advanced, respecting the physical constitution of the Sun, there 
is none entirely free from objection. The prevailing one seems 
to be, that the lucid matter of the Sun is neither a liquid sub- 
stance, nor an elastic fluid, but that it consists of luminous 
clouds, floating in the Sun's atmosphere, which extends to a 
great distance, and that these dark spots are the opaque body 
of the Sun, seen through the openings in his atmosphere. Her- 
schel supposes that the density of the luminous clouds need not' 
be greater than that of our Aurora Borealis, to produce the 
effects with which we are acquainted. 

339. The similarity of the Sun to the other globes of the sys- 
tem, in its supposed solidity, atmosphere, surface diversified with 
mountains and valleys, and rotation upon its axis, has led to the 
conjecture that it is inhabited, like the planets, by beings whose 
organs are adapted to their peculiar circumstances. Such was 
the opinion of the late Dr. Herschel, who observed it unremit- 
tingly, with the most powerful telescopes, for a period of fifteen 
years. Such, too, was the opinion of Dr. Elliot, who attributes 
to it the most delightful scenery ; and, as the light of the Sun 
is eternal, so, he imagined, were its seasons. Hence he infers 
that this luminary offers one of the most blissful habitations for 
intelligent beings of which we can conceive. 

337. Laplace's speculations? What other opinions? 338. Is there a satisfactory- 
theory of the physical nature of the Sun? State the prevailing one ? Herschel's suppo- 
sition? 339. What conjecture in regard to the inhabitants of the Sun, and upon 
what founded? Who held to this idea? 



THE PRIMARY PLANETS MERCURY AND VENUS. 177 

CHAPTER III. 

THE PEIMAEY PLANETS— MERCUKY AND VENUS. 

340. Mercury is the nearest planet to the Sun that has yet 
been discovered ; and with the exception of the asteroids, is tlu 
smallest. Its diameter is only 3,140 miles. Its bulk, therefore, 
is about sixteen times less than that of the Earth. It would 
require more than twenty millions of such globes to compose a 
body equal to the Sun. 

Here the student should refer to the diagrams, exhibiting the relative magnitudes and 
distances of the Sun and Planets, Map I. And whenever this subject recurs in the course 
of this work, the student should recur to the figures of this Map, until he is able to form 
in his mind distinet conceptions of tne relative magnitudes and distances of all the 
planets. The Sun and planets being spheres, or nearly so, their relative bulks are esti- 
mated by comparing the cubes of their diameters : thus, the diameter of Mercury being 
3,140 miles, and that of the Earth 7,912 ; their bulks are as the cube of 3,140, to the cube 
of 7,912, or as 1 to 16, nearly. 

341.. Mercury revolves on its axis from west to east in 24 
hours, 5 minutes, and 28 seconds ; which makes its day about 
10 minutes longer than ours. It performs its revolution about 
the Sun in a few minutes less than 88 days, and at a mean dis- 
tance of nearly 31,000,000 of miles. The length of Mercury's 
year, therefore, is equal to about three of our months. 

The rotation of a planet on its axis, constitutes its day; its revolution about the Sua 
joustitutes its year. 

342. Owing to the dazzling brightness of Mercury, the swift- 
ness of its motion, and its nearness to the Sun, astronomers 
have made but comparatively few discoveries respecting it. 
When viewed through a telescope of considerable magnifying 
power, it exhibits at different periods all the various phases of 
the Moon ; except that it never appears quite full, because its 
enlightened hemisphere is never turned directly towards the 
Earth, only when it is behind the Sun, or so near to it as to be 
hidden by the splendor of its beams. Its enlightened hemisphere 
being thus always turned towards the Sun, and the opposite one 
being always dark, prove that it is an opaque body, similar to 
the Earth, shining only in the light which it receives from the 
Sun. 

343. Mercury is not only the most dense of all the planets, 
but receives from the Sun six and a half times as much light and 

340. Subject of Chapter III. ? Size and position of Mercury? What map illustrates 
this subject? 341. State the time of Mercury's revolution upon his axis? How does 
this compare with the Earth ? His period of revolution around the Sun ? 342. What 
said of discoveries upon Mercury, his phases, &c. ? What proof that he is opaque ? 



178 



ASTRONOMY 



heat as the Earth. The truth of this estimate, of course, 
depends upon the supposition that the intensity of solar light and 
heat at the planets, varies inversely as the squares of their dis- 
tances from the Sun. 



PHILOSOPHY OF THE DIFFUSION OF LIGHT. 




In this diagram the light is seen passing in right lines, from the sun on the left toward 
the several planets on the right. It is also shown that the surfaces A, B, and C receive 
equal quantities of light, though B is four times, and C nine times as large as A; and as 
the light falling upon A is spread over four times as much surface at B, and nine times as 
much at C, it follows that it is only one-ninth as intense at C, and one-fourth at B, as it 
is at A. Hence the rule, that the light and heat of the planet is, inversely, as the squares 
of their respective distances. 

The student may not exactly understand this last statement. The square of any num- 
ber is its product, when multiplied by itself. Now suppose we call the distances A, B, 
and C, 1, 2, and 3 miles. Then the square of 1 is 1 ; the square of 2 is 4; and the square 
of 3 is 9. The light and heat, then, would be in inverse proportion at these three points, 
as 1, 4, and 9 ; that is, four times less at B than at A, and nine times less at C. The?e 
amounts we should state as 1, \, and one-ninth. 

344. This law of analogy, did it exist with rigorous identity 
at all the planets, would be no argument against their being 
inhabited ; because we are bound to presume that the All-wise 
Creator has attempered every dwelling-place in his empire to the 
physical constitution of the beings which he has placed in it. 

From a variety of facts which have been observed in relation to the production of 
caloric, it does not appear probable, that the degree of heat on the surface of the differ- 
ent planets depends on their respective distances from the Sun. It is more probable, that 
it depends chiefly on the distribution of the substance of caloric on the surfaces, and 
throughout the atmospheres of these bodies, in different quantities, according to the dif- 
ferent situations which they occupy in the solar system ; and that these different quan- 
tities of caloric are put into action by the influence of the solar rays, so as to produce 
that degree of sensible heat requisite to the wants, and to the greatest benefit of each of 
the planets. On this hypothesis, which is corroborated by a great variety of facts and 
experiments, there may be no more sensible heat experienced on the planet Mercury, 
than on the surface of Herschel, which is fifty times farther removed from the Sun. 

345. The rotation of Mercury on its axis, was determined 
from the daily position of its horns, by M. Schroeter, who not 
only discovered spots upon its surface, but several mountains in 
its southern hemisphere, one of which was lOf miles high — - 
nearly three times as high as Chimborazo, in South America. 

343. His density, and light and heat? Upon what rule is this estimate based? 344. 
Would not this law of analogy make against the doctrine that the planets are inhab- 
ited ? Is it probable that this law does prevail? Upon what may the relative heat of the 
planets depend? 345. How was his diurnal revolution determined, and by whom? 
What said of his surface ? What observation respecting mountains in general ? 



THE PRIMARY PLANETS MERCURY AND VENUS. 179 

It is worthy of observation, that the highest mountains which have been discovered in 
Mercury, Venus, the Moon, and perhaps we may add the Earth, are all situated in their 
southern hemispheres. 

346. During a few days in March and April, August and Sep- 
tember, Mercury may be seen for several minutes, in the morn- 
ing or evening twilight, when its greatest elongations happen in 
those months ; in all other parts of its orbit, it is too near the 
Sun to be seen by the naked eye. The greatest distance that it 
ever departs from the Sun, on either side, varies from 16° 12', 
to 28° 48', alternately. 

The distance of a planet from the Sun, as seen from the Earth 
(measured in degrees), is called its elongation. The greatest 
absolute distance of a planet from the Sun is denominated its 
aphelion, and the least its perihelion. 

34 T. The revolution of Mercury about the Sun, like that of 
all the planets, is performed from west to east, in an orbit which 
is nearly circular. Its apparent motion, as seen from the Earth, 
is, alternately, from west to east, and from east to west, nearly 
in straight lines ; sometimes directly across the disc of the Sun, 
but at all other times either a little above or a little below it. 

Were the orbits of Mercury and Venus in the same plane with that of the Earth, they 
would cross the Sun's disc at every revolution ; but as one-half of each of their orbits is 
above, and the other half below the ecliptic, they generally appear to pass either above 
or below the Sun. 

B ^ "'"" D 

J"^" ■z-~--- :: ---"":::::i'. " W 

^ »» ^^ jj 

Let the right line A, joining the Earth and the Sun in the above diagram, represent 
the plane of the ecliptic. Now when an interior planet is in this plane, as shown at A, 
it may appear to be upon the Sun's disc ; but if it is either above or below the ecliptic, 
as shown at B and C, it will appear to pass either above or below the Sun, as shown at 
I) and E. 

For the relative position of the planets' orbits, and their inclination to the plane of the 
ecliptic, see 1, of the Atlas. Here the dotted lines continued from the dark lines, 
denote the inclination of the orbits to the plane of the ecliptic, which inclination is 
marked in figures on them. Let the student fancy as many circular pieces of paper 
intersecting each other at the several angles of inclination marked on the Map, and he 
will be enabled to understand more easily what is meant by the " inclination of the 
planets' orbits." 

348. Being commonly immersed in the Sun's rays in the even- 
ing, and thus continuing invisible till it emerges from them in 
the morning, Mercury appeared to the ancients like two distinct 
stars. A long series of observations was requisite, before they 

346. When may Mercury be seen? Why not at other times? How far does it depart 
from the Sun on either side? What is meant by the elongation of a planet ? Its aphe- 
lion and perihelion ? 347. In what direction do the planets revolve around the Sun ? 
What is the apparent motion of Mercury ? Do they ever cross the Sun's disc ? Why 
not at every revolution ? 848. How was Mercury regarded by the ancients ? 

8* 



180 



ASTRONOMY. 



recognized the identity of the star which was seen to recede 
from the Sun in the morning with that which approached it in 
the evening. But as the one was never seen until the other 
disappeared, both were at last found to be the same planet, which 
thus oscillated on each side of the Sun. 

349. Mercury's oscillation from west to east, or from east to 
west, is really accomplished in just half the time of its revolution, 
which is about 44 days ; but as the Earth, in the mean time, 
follows the Sun in the same direction, the apparent elongations 
will be prolonged to between 55 and 65 days. 

350. The passage of Mercury or Yenus directly between the 
Earth and the Sun, and apparently over his disc, is called a 
Transit. A transit can never occur except when the interior 
planet is in or very near the ecliptic. The Earth and the planet 
must be on the same side of the ecliptic ; the planet being at 
one of its nodes, and the Earth on the line of its nodes. 



PHILOSOPHY OF TRANSITS. 

L 




This cut represents the ecliptic and zodiac, with the orbit of an interior planet, his 
node's, &c. The line of his nodes is, as shown, in the 16° of » and the 16° of Tli. Now if 
the earth is in 8 , on the line L N, as shown in the cut, when Mercury is at his ascending 
node (Q), he will seem to pass upward over the Sun's face, like a dark spot, as repre- 
sented in the figure. On the other hand, if Mercury is at his descending node (y), 
when the earth is in the 16° of m,, the former will seem to pass downward across the 
disc of the Sun. 

351. As the nodes of his orbit are on opposite sides of the 
ecliptic, and are passed by the Earth in May and November, it 
follows that all transits of Mercury must occur in one or the 
other of these months. They are, therefore, called the Node 
months. As is shown in the diagram, the Earth passes the 

349. In what time is the oscillation of Mercury from east to west really accomplished? 
What is the apparent time, and why ? 350. What is a transit ? When do they occur ? 
What are the nodes of a planet's orbit? The line of the nodes? 851. What are the 



THE PRIMARY PLANETS MERCURY AND VENUS. 181 



TKANSITS OF MERCUBY. 

NORTH 



ascending Node of Mercury in November, and the descending in 
May ; the former of which is in the 16th degree of Taurus, and 
the latter in the 16th degree of Scorpio. 

All the transits of-Mercury ever noticed have occurred in one or the other of these 
months, and for the reason already assigned. The first ever observed took place Novem- 
ber 6, 1631 ; since which time there have been 29 others by the same planet — in all 30— 
8 in May, and 22 in November. 

352. The last transit of Mercury occurred November 9, 1848; 
and the next will take place November 11, 1861. Besides this, 
there will be five more during the present century — two in May, 
and three in November. 

The accompanying cut is a de- 
lineation of all the transits of Mer- 
cury from 1802 to the close of the 
present century. The dark line 
running east and west across the 
Sun's center represents the plane 
of the ecliptic, and the dotted lines 
the apparent paths of Mercury in 
the several transits. The planet 
is shown at its nearest point to the 
Sun's center. Its path in the last 
transit and in the next will easily 
be found. 

The last transit of Mercury was 
observed in this country by Pro- 
fessor Mitchel, at the Cincinnati 
Observatory, and by many others 
both in America and in Europe. 
The editor had made all necessary 
preparation for observing the phe- 
nomenon at his residence, near 
Oswego, New York ; but, unfor- 
tunately, his sky was overhung 
with clouds, which hid the sun 
from his view, and disappointed all 
his hopes. 

353. By comparing the mean motion of any of the planets 
with the mean motion of the Earth, we may readily determine 
the periods in which they will return to the same points of their 
orbit, and the same positions with respect to the Sun. The 
knowledge of these periods will enable us to determine the hour 
when the planets rise, set, and pass the meridian, and in general 
all the phenomena dependent upon the relative position of the 
Earth, the planet and the Sun ; for at the end of one of these 
periods they commence again, and all recur in the same order. 

We have only to find a number of sidereal years, in which the planet completes 
exactly, or very nearly, a certain number of revolutions ; that is, to find such a number 
of planetary revolutions, as, when taken together, shall be exactly equal to one, or any 
number of revolutions of the Earth. In the case of Mercury this ratio will be as 87.969 
is to 365.256. Whence find that, 

node months of a planet? The node months of Mercury? 352. When did the last 
transit of Mercury occur? When will the next take place? What others during the 
present century? What said of the last transit of Mercury ? 353. How may we deter- 
mine when transits will occur? What ratio is found between the revolutions of Mercury 




SQVTH 



182 



ASTRONOMY. 



7 periodical revolutions of the Earth are equal to 29 of Mercury : 
13 periodical revolutions of the Earth are equal to 54 of Mercury: 
33 periodical revolutions of the Earth are equal to 137 of Mercury : 
46 periodical revolutions of the Earth are equal to 191 of Mercury. 

Therefore, transits of Mercury, at the same node, may happen at intervals of 7, 13, 33, 46, 

&c. years. Transits of Venus, as well as eclipses of the Sun and Moon, are calculated 

upon the same principle. 
The following is alist of all the Transits of Mercury from the time the first was observed 

by G-assendi, November 6, 1631, to the end of the present century : 



1631 Nov. 6. 
1644 Nov. 6. 
1651 Nov. 2. 
1661 May 3. 
1664 Nov. 4. 
1674 May 6. 
1677 Nov. 7. 
1690 Nov. 9. 
1697 Nov. 2. 



1707 May 5. 

1710 Nov. 6. 

1723 Nov. 9. 
1736 Nov. 10. 

1740 Nov. 2. 

1743 Nov. 4. 

1753 May 5. 

1756 Nov. 6. 

1769 Nov. 9. 



1776 Nov. 2. 
1782 Nov. 12. 
1786 May 3. 
1789 Nov. 5. 
1799 May 7. 
1802 Nov. 8. 
1815 Nov. 11. 
1822 Nov. 4. 
1832 May 5. 



1835 Nov. 7. 
1845 May 8. 
1848 Nov. 9. 
1861 Nov. 11. 
1868 Nov. 4. 
1878 May 6. 
1881 Nov. 7. 
1891 May 9. 
1894 Nov. 10. 



E D 
..-© ©-.., 



354. The sidereal revolution of a planet respects its absolute 
motion ; and is measured by the time the planet takes to revolve 
from any fixed star to the same star again. The synodical revo- 
lution of a planet respects its relative motion ; and is measured 
by the time that a planet occupies in coming back to the same 
position with respect to the Earth and the Sun. 

SIDEREAL AND SYNODIC REVOLUTIONS. 

m In the adjoining cut the revolution of 

,.-•-'" "*"***•-•. the Earth from A, opposite the star B, 

,--"'' **•.. around to the same point again, would be 

a sidereal revolution. 

Suppose the Earth and Mercury to start 
together from the points A C (where Mer- 
cury would be in inferior conjunction with 
the Sun), and to proceed in the direction 
of the arrows. In 88 days Mercury would 
come around to the same point again ; 
but as the Earth requires more than four 

i \&r —<r- ^ times that number of days for a revolu- 

\ /' / ^""*— -/r t ' on ' sne wil1 on 'y nave reached the point 

s «x^ --'* / / 7 D when Mercury arrives at C again; so 

that they will not be in conjunction, and a 
synodic revolution will not be completed 
by Mercury. He starts on, however, in 
his second round, and constantly gaining 
upon the Earth, till in 27 days from the 
time he left C the second time, he over- 

"*■*•• — -"""" takes the Earth at E and F, and is again in 

inferior conjunction, 
from this illustration, it will be seen that the synodic revolution of a planet must 
always require more time than the sidereal. 

355. The absolute motion of Mercury in its orbit is 1 09,151 
miles an hour ; that of the Earth is 68,288 miles ; the differ- 
ence, 41,469 miles, is the mean relative motion of Mercury, with 
respect to the Earth. 

The sidereal revolution of Mercury is 87d. 23h. 15m. 44s. Its synodical revolution 13 

and the Earth? 354. What is a sidereal revolution of a planet? A synodical? 
355. What is the absolute motion of Mercury in his orbit? What is that of the Earth ? 
The difference, or relative motion of Mercury? What js his sidereal period? Hi3 
synodic t How Is the latter ascertained? 



? 9~ — : 



\ 



V 



/ 



V 



THE PRIMARY PLANETS MERCURY AND VENUS. 183 

found by dividing the whole circumference of 360° by its relative motion in respect to the 
Earth. Thus, the mean daily motion of Mercury is 14732". 555; that of the Earth is 
3548" .318 ; and their difference is 11184\237, being Mercury's relative motion, or what it 
gains on the Earth every day. Now by simple proportion, 11184".237 is to 1 day, as 360° 
is to 115d. 21h. 3', 24", the period of a synodical revolution of Mercury. 



VENUS. 

356. There are but few persons who have not observed a 
beautiful star in the west, a little after sunset, call the evening 
star. This star is Venus. It is the second planet from the 
Sun. It is the brightest star in the firmament, and on this 
account easily distinguished from the other planets. 

If we observe this planet for several days, we shall find that 
it does not remain constantly at the same distance from the Sun, 
but that it appears to approach, or recede from him, at the rate 
of about three-fifths of a degree every day ; and that it is some- 
times on the east side of him, and sometimes on the west, thus 
continually oscillating backwards and forwards between certain 
limits. 

35t. As Venus never departs quite 48° from the Sun, it is 
never seen at midnight, nor in opposition to that luminary ; 
being visible only about three hours after sunset, and as long 
before sunrise, according as its right ascension is greater or less 
than that of the Sun. At first, we behold it only a few minutes 
after sunset ; the next evening we hardly discover any sensible 
change in its position ; but after a few days, we perceive that 
it has fallen considerably behind the Sun, and that it continues 
to depart farther and farther from him, setting later and later 
every evening, until the distance between it and the Sun is 
equal to a little more than half the space from the horizon to the 
zenith, or about 46°. It now begins to return toward the Sun, 
making the same daily progress that it did in separating from 
him, and to set earlier and earlier every succeeding evening, 
until it finally sets with the Sun, and is lost in the splendor of 
his light. 

358. A few days after the phenomena we have now described, 
we perceive, in the morning, near the eastern horizon, a bright 
star which was not visible before. This also is Venus, which is 
now called the morning star. It departs farther and farther 
from the Sun, rising a little earlier every day, until it is seen 

356. Describe Venus. What called ? Distance from the Sun ? What change of posi- 
tion observable ? 357. Greatest distance to which she departs from the Sun? What 
consequence ? How and when seen ? 358. What next after these phenomena ? 



184 ASTRONOMY. 

about 46° west of him, where it appears stationary for a few 
days ; then it resumes its course towards the Sun, appearing 
later and later every morning, until it rises with the Sun, and 
we cease to behold it. In a few days, the evening star again 
appears in the west, very near the setting sun, and the same 
phenomena are again exhibited. Such are the visible appear- 
ances of Yenus. 

359. Yenus revolves a-bout the Sun from west to east in 224 J 
days, at the distance of about 68,000,000 of miles, moving in 
her orbit at the rate of 80,000 miles an hour. She turns 
around on her axis once in 23 hours, 21 minutes, and T seconds. 
Thus her day is about 25 minutes shorter than ours, while her 
year is equal to ?■§■ of our months, or 32 weeks. 

360. The mean distance of the Earth from the Sun is estimated 
at 95,000,000 of miles, and that of Yenus being 68,000,000, 
the diameter of the Sun, as seen from Yenus, will be to his 
diameter as seen from the Earth, as 95 to 68, and the surface 
of his disc as the square of 95 to the square of 68, that is, 
as 9025 to 4626, or as 2 to 1, nearly. The intensity of light 
and heat being inversely as the square of their distances from 
the Sun (No. 342), Yenus receives twice as much light and heat 
as the Earth. 

361. The orbit of Yenus is within the orbit of the Earth ; 
for if it were not, she would be seen as often in opposition to the 
Sun, as in conjunction with him ; but she was never seen rising 
in the east while the Sun was setting in the west. Nor was she 
ever seen in quadrature, or on the meridian, when the Sun was 
either rising or setting. Mercury's greatest elongation being 
about 23° from the Sun, and that of Yenus about 46°, the orbit 
of Yenus must be outside of the orbit of Mercury. 

362. The true diameter of Yenus is 1100 miles ; but her 
apparent diameter and brightness are constantly varying, accord- 
ing to her distance from the Earth. When Yenus and the 
Earth are on the same side of the Sun, her distance from the 
Earth is only 26,000,000 of miles ; when they are on opposite 
sides of the Sun, her distance is 164,000,000 of miles. Were 
the whole of her enlightened hemisphere turned towards us, 
when she is nearest, she would exhibit a light and brilliancy 



359. What is Venus' sidereal period? Distance from the Sun? Rate of motion? 
Time of rotation upon her axis? How, then, do her day and year compare with ours ? 

360. How must the Sun appear from Venus, and why? What of her light and heat? 

361. Where is the orbit of Venus situated? What proof of this? 362. Venus' diame- 
ter ? Her apparent diameter ? State her least and greatest distances from the Earth? 



THE PRIMARY PLANETS MERCURY AND VENUS. 185 

twenty-five times greater than she generally does, and appear 
like a small brilliant moon ; but, at that time, her dark hemi- 
sphere is turned towards the Earth. 

When A 7 enus approaches nearest to the Earth, her apparent, or observed diameter is 
61\2; when most remote, it is only 9°. 6 ; now 61*.2-s-9'.6=6%, hence when nearest the 
Earth her apparent diameter is 6% times greater than when most distant, and surface 
of her disc (6%°j>- or nearly 41 times greater. In this work, the apparent size of the 
heavenly bodies is estimated from the apparent surface of their discs, which is always 
proportional to the squares of their apparent diameters. 

363. Mercury and Yenus are called Interior planets, because 
their orbits are within the Earth's orbit, or between it and the 
Sun. The other planets are denominated Exterior, because their 
orbits are without or beyond the orbit of the Earth. (Map I.) 
As the orbits of Mercury and Yenus lie within the Earth's orbit, 
it is plain, that once in every synodical revolution, each of these 
planets will be in conjunction on the same side of the Sun. In 
the former case, the planet is said to be in its inferior conjunc- 
tion, and in the latter case, in its superior conjunction ; as in the 
following figure. 

MARS IN CONJUNCTION _ , , . . - . . 

. — s- Let the student imagine him- 

„.«.-*""" ^ "*►.» self stationed upon the earth in 

y* \ the cut. Then the sun and three 

___ \ planets above are in conjunc- 

/ ,.--- \ Hon. The inferior and supe- 

N \ * rior are distinguished ; while at 

A, a planet is shown in quadra- 

\ ture, and at the bottom of the 

cut the planet Mars in opposi- 

\ tion with the sun and interior 

\ \ planet. 

'l \ The period of Venus' synodi- 

i ! cal revolution is found in the 

I same manner as that of Mer- 

/ ; cury ; namely, by dividing the 

• J whole circumference of her orbit 

/ by her mean relative motion in 

/ / a day. Thus, Venus' absolute 

\\ ~"~~-Q — '' / / mean daily motion is 1° 36' 7".S, 

'A/rELBAO* / / the Earth's is 59' 8".-3, and their 

S. y y / difference is 36' 59".o. Divide 

*--.. ^ ^.-'' / 360° by 36' 59".5, and it gives 

\ *"*""<!? ' /' 583.920, or nearly 5S4 days for 

v, y Venus' synodical revolution, or 

"^*-.., <5> ^*r''' the period in which she is 

"" © • — twice in conjunction with the 

MARS IN OPEQS.ItlON Earth. 

364. When Yenus' right ascension is less than that of the 
Sun, she rises before him ; when greater, she appears after hia 
setting. She continues alternately morning and evening star, 
for a period of 292 days, each time. 

How would she appear if we saw her enlightened side when nearest to us? What com- 
putation in the fine print ? 363. How are Mercury and Venus distinguished, and why? 
What said of conjunctions f Describe the inferior and superior ? How is the period of 
Venus' synodical revolution found? 864. When is Venus evening star? Morning? 



/ 


/ 


s 


SUPERfO# 


/ / 






,.--©--. 




/" 


6 


/ / 




/ 




; ; 








Ip 1 

?A \ 








\ \ 




\ 




\ 
\ 




V 


6 



186 



ASTRONOMY. 



To those who are but little acquainted with astronomy, it will seem strange, at first, 
that Venus should apparently continue longer on the east or west side of the Sun, than 
the whole time of her periodical revolution around him. But it will be easily understood, 
when it is considered, that while Venus moves around the Sun, at the rate of about 1* 36' 
of angular motion per day, the Earth follows at the rate of 59' ; so that Venus actually 
gains on the Earth, only 37' in a day. 

Now it is evident that both planets will appear to keep on the same side of the Sun, 
until Venus has gained half her orbit, or 180° in advance of the Earth; and this, at a 
mean rate, will require 292 days, since 292 x 37' =10804', or 180" nearly. 

365. Terms passes from her inferior to her superior conjunc- 
tion in about 292 days. At her inferior conjunction, she is 
26,000,000 of miles from the Earth ; at her superior conjunc- 
tion, 164,000,000 of miles. It might be expected that her bril- 
liancy would be proportionally increased, in the one case, and 
diminished in the other ; and so it would be, were it not that 
her enlightened hemisphere is turned more and more from us, as 
she approaches the Earth, and comes more and more into view 
as she recedes from it. It is to this cause alone that ^ e must 
attribute the uniformity of her splendor, as it usually appears to 
the naked eye. 

366. Mercury and Yenus present to us, successively, the 
various shapes and appearances of the Moon ; waxing and 
waning through different phases, as shown in the following cut, 
from the beautiful crescent to the full rounded orb. This fact 
shows, that they revolve around the Sun, and between the Sun 
and the Earth. 





PHASES OP VENUS AS SHE REVOLVES AROUND THS SUN. 


- . ' gj 


jjgjjjjjj 


u 


mi 


~^^mi 


jj 


Np 


^z: ==^==|^g^_ frr =~ _^^gr^[ )' J 


kJu 




E 


ndtfjiij 


- — j 


8 


[=-== 




- ■ , • J^=^=L= 



It should be remarked, however, that Venus is never seen when she is entirely full, 
except once or twice in a century, when she passes directly over the Sun's disc. At 
every other conjunction, she is either behind the Sun, or so near him as to be hidden by 
the splendor of his light. The preceding diagram better illustrates the various appear- 
ances of Venus, as she moves around the Sun, than any description of them could do. 

367. From her inferior to her superior conjunction, Yenus, 
appears on the west side of the Sun, and is then our morning 

How long each? How is it that Venus is east or west of the Sun 292 days, when her 
periodic revolution is performed in about 225 days ? 365. What is the time from one 
conjunction of Venus to another? Is her brilliancy in proportion to her nearness? Why 
not? 366. What phases do Mercury and Venus exhibit, and what do they prove? 
Are they ever seen entirely full t 867. When is Venus morning star? When evening? 



THE PRIMARY PLANETS MERCURY AND VENUS. 



181 



star • from her superior to her inferior conjunction she appears 
on the east side of the Sun, and is then our evening star. These 
phenomena are illustrated by the following diagram. 



VENUS AS MORNING AND EVENING STAR. 



M 



X 



A«//> 



ji ^I.-t%-^?r If 




T et the student hold the book up south of him, and he will at once see why Venus is 
alternately ^moTning and evening star. Let the plane A B represent the sensible or Risi- 
ble ^horizon CD the apparent daily path of the Sun through the heavens and E the 
Farth in her anna! ent position The Sun is shown at three different points-namely, 
Sh g in Ue S n h meridian, and setting in the west ; while Venus is seen revolving 
ai^und him from'west to east, or in the direction of the arrows Now i « jbyious that 
when Venus is at F or west of the Sun, she sets before him as at 0, and uses beloie mm 
Is a? H She must therefore, be morning star. On the other hand, when she is east 
ol the Sun; as 5™ she lingers in the west after the Sun has gone down, as at K, and is 

C TnZr C u?, VeTus wSd-be at her greatest elongation eastward at J, and vvrtuard 
at F, and in both cases would be » stationary .» At L and M she would be in conjxmc 

^WeTethelarthto suspend her daily rotation, with the Sun on the meridian of the 
obSr e r,Lr^,presented P at L, we might readily watch Venus through her whole circurt 
around the Sun. 

368. Like Mercury, Yenus sometimes seems to be stationary. 
Her apparent motion, like his, is sometimes rapid ; at one time, 
direct and at another, retrograde; vibrating alternately back- 
wards and forwards, from west to east, and from east to west. 
These vibrations appear to extend from 45° to 47°, on each side 
of the Sun. 

Consequently she never appears in the eastern horizon more than three hours before 
suniise!n 01 continues longer in the western horizon after sunset Any star or planet 
therefore, however brilliant it may appear, which is seen earlier or later than this, cannot 
be Venus. 

369. In passiDg from her western to her eastern elongation, 

"268. Is she ever stationary? What other irregularities in her apparent motion? 
369 When is her motion direct t When retrograde? When most rapid? Whep 



188 



ASTRONOMY. 




her motion is from west to east, in the order of the signs ; it is 
thence called direct motion. In passing from her eastern to her 
western elongation, her motion with respect to the Earth is 
from east to west, contrary to the order of the signs ; it is 
thence denominated retrograde motion. Her motion appears 
quickest about the time of her conjunctions ; and she seems sta- 
tionary at her elongations. She is brightest about thirty-six 
days before and after her inferior conjunction, when her light is 
so great as to project a visible shadow in the night, and some- 
times she may be seen with the naked eye even at noon-day. 

DIRECT AND RETROGRADE MOTI02TS. 

The cause of the apparent re- 
trogression of the interior planets 
is the fact that they revolve much 

\more rapidly than the earth, from 
\ / which we view them ; causing 

\ / their direct motion to appear to 

be retrograde. 

Suppose the earth to be at A, and Venus at 
B, she would appear to be at C, among the 
stars. If the earth remained at A while 
Venus was passing from B to D, she would 
seem to retrograde from C to E; but as the 
earth passes from A to F while Venus goes 
from B to D, Venus will appear to be at O ; 
and the amount of her apparent westward 
motion will only be from C to G-. 

370. If the orbit of Yenus lay 
exactly in the plane of the Earth's 
orbit, she would pass centrally 
across the Sun's disc, like a dark 
round spot, at every inferior conjunction ; but, as one-half 
of her orbit lies about 3-*-° above the ecliptic, and the other half 
as far below it, she will always pass the Sun a very little above 
or below it, except when her inferior conjunction happens in, or 
near one of her nodes ; in which case she will make a transit. 
(See cuts, pages 179 and 180.) 

This phenomenon, therefore, is of very rare occurrence ; it can 
happen only twice in a century ; because it is only twice in that 
time that any number of complete revolutions of Venus are just 
or nearly equal to a certain number of the Earth's revolutions. 

The principle which was illustrated in predicting the transits of Mercury, applies 
equally well to those of Venus ; that is, we must find such sets of numbers (representing 

brightest? State the cause of the apparent retrograde motion? 370. Why have we not 
a transit at every revolution of Venus? How frequent, therefore? How predicted? 
When do her nodes cut the ecliptic? 




THE PRIMARY PLANETS MERCURY AND VENUS. 189 

complete revolutions of the Earth and Venus) as shall be to each other in the ratio of 
their periodical times, or as 365.256 is to 224.7. Thus : the motion of Venus, in the Julian 
years, is 2106591".52 ; that of the Earth for the same period being 129627".45, the ratic 
will be 2J JULJULJ "-|-|-. As the two terms of this fraction cannot be reduced by a com- 
mon divisor, we must multiply them by such numbers as will make one a multiple of the 
other ; accordingly, 13 times the denominator will be nearly equal to S times the nume- 
rator ; and 475 times the denominator will equal 291 times the numerator. 

By combining these two periods and their multiples by addition and subtraction, we 
shall obtain the period of all the transits that have ever happened. Thus : 291—8 x 7=235, 
another period ; and 291 — 6x8=243, another period, and so on. Whence we find that 
8 periodical revolutions of the Earth are equal to 13 of Venus : 
235 periodical revolutions of the Earth are equal to 3S2 of Venus : 
243 periodical revolutions of the Earth are equal to 395 of Venus : 
251 periodical revolutions of the Earth are equal to 40S of Venus : 
291 periodical revolutions of the Earth are equal to 475 of Venus. 
Hence a transit of Venus may happen at the same node, after an interval of 8 years ; 
but if it do not happen then, it cannot take place again at the same node, in less than 
235 years. The orbit of Venus crosses the ecliptic near the middle of Gemini and Sagit- 
tarius ; and these points mark the position of her nodes. At present, her ascending node 
is in the 14th degree of Gemini, and her descending node in the same degree of Sagit- 
tarius. 

371. The node months of Venus are December and June. 
The line of her nodes lies in Gemini ( n ) and Sagittarius ( £ ) ; 
and as the Earth always passes those points in the months 
named, it follows that all transits of Venus must occur in those 
mouths for ages to come. 

This proposition will be well understood by consulting the cut on page ()Oo ; for as the 
line of Venus' nodes is only one sign ahead of that of Mercury, the Earth will reach 
that point in the ecliptic in one month after she passes the line of Mercury's nodes ; so 
that if his transits occur in May and November, hers should occur in June and December, 
as is always the case. 

272. The first transit ever known to have been seen by any 
human being, took place at the ascending node, December 4th, 
1639.* If to this date we add 235 years, we shall have the 

* This phenomenon was first witnessed by Horrox, a young gentleman about 21 years 
of age, living in an obscure village 15 miles north of Liverpool. The tables of Kepler, 
constructed upon the observations of Tycho Brahe, indicated a transit of Venus in 1631, 
but none was observed. Horrox, without much assistance from books and instruments, 
set himself to inquire into the error of the tables, and found that such a phenomenon 
might be expected to happen in 1639. He repeated his calculations during this interval, 
with all the carefulness and enthusiasm of a scholar ambitious of being the first to predict 
and observe a celestial phenomenon, which, from the creation of the world, had never 
been witnessed. Confident of the result, he communicated his expected triumph to a 
confidential friend residing in Manchester, and desired him to watch for the event, and 
to take observations. So anxious was Horrox not to fail of witnessing it himself, that he 
commenced his observations the day before it was expected, and resumed them at the 
rising of the Sun on the morrow. But the very hour when his calculations led him to 
expect the visible appearance of Venus on the Sun's disc, was also the appointed hour 
for the public worship of God on the Sabbath. The delay of a few minutes might 
deprive him for ever of an opportunity of observing the transit. If its very commence- 
ment were not noticed, clouds might intervene, and conceal it until the Sun should set: 
and nearly a century and a half would elapse before another opportunity would occur. 
He had been waiting for the event with the most ardent anticipation for eight years, and 
the result promised much benefit'to the science. Notwithstanding all this, Horrox 
twice suspended his observations and twice repaired to the House of God, the Great 
Author of the bright works he delighted to contemplate. When "his duty was thus per- 

871. Which are her node months ? 372. When was the first transit observed ? What 
interesting anecdote ? 



190 ASTRONOMY. 

time of the next transit at the same node, which will accordingly 
happen in 18? 4. There will be another at the same node in 
1882, eight years afterwards. It is not more certain that this 
phenomenon will recur, than that the event itself will engross 
the attention of all the astronomers then living upon the Earth. 
It will be anticipated, and provided for, and observed, in every 
inhabited quarter of the globe, with an intensity of solicitude 
which no natural phenomenon, since the creation, has ever 
excited. 

313. The reason why a transit of Yenus should excite so great 
an interest is, because it may be expected to solve an important 
problem in astronomy, which has never yet been satisfactorily 
done : — a problem whose solution will make known to us the 
magnitudes and masses of all the planets, the true dimensions of 
their orbits, their rates of motion around the Sun, and their 
respective distances from the Sun, and from each other. It may 
be expected, in short, to furnish an universal standard of astro- 
nomical measure. Another consideration will render the obser- 
vation of this transit peculiarly favorable ; and that is, astrono- 
mers will be supplied with better instruments, and more accurate 
means of observation, than on any former occasion. 

So important, says Sir John Herschel, have these observations appeared to astronomers, 
that at the last transit of Venus, in 1769, expeditions were fitted out, on the most efficient 
scale, by the British, French, Russian, and other governments, to the remotest corners of 
the globe, for the express purpose of making them. The celebrated expedition of Captain 
Cook to Otaheite, was one of them. The general result of all the observations made on 
this most memorable occasion, gives 8". 5776 for the Sun's horizontal parallax. 

314. The phenomena of the seasons of each of the planets, 
like those of the Earth, depend upon the inclination of the axis 
of the planet to the plane of its orbit, and its revolution around 
the Sun. The inclination of the axis of Yenus to the plane of 
her orbit, though not precisely known, is commonly estimated at 
15°, as represented to the eye in the following cut : 



formed, and he had returned to his chamber the second time, his love of science was 
gratified with full success ; and he saw what no mortal eye had observed before ! 

If anything can add interest to this incident, it is the modesty with which the young 
astronomer apologizes to the world, for suspending his observations at all. 

" I observed it," says he, " from sunrise till nine o'clock, again a little before ten, and 
lastly at noon, and from one to two o'clock ; the rest of the day being devoted to higher 
duties, which might not be neglected for these pastimes." 

When the next? When another? How will it be regarded? 373. Why should such 
an event excite general interest? Remark of Sir John Herschel ? What expedition and 
what results? 374. Upon what do the seasons of the planets depend? What is the 
inclination of Venus' axis to the plane of her orbit? How is her orbit situated with 
reference to the ecliptic? 



THE PRIMARY PLANETS MERCURY AND VENUS. 191 

ISCLI1IATI0N OF VKN0S' AXIS. 



<n> 




The orbit of Venus departs from the ecliptic 3^°, while her axis is inclined to the 
plane of her orbit 75°, as shown in the above figure. This distinction should be kept 
definitely in view by the student. 

375. The declination of the Sun on each side of Yenus' equa- 
tor, must be equal to the inclination of her axis ; and if this 
extends to 75°, her tropics are only 15° from her poles, and her 
polar circles only 15° from her equator. It follows, also, that 
the Sun must change his declination more in one day at Yenus, 
than in five days on the Earth ; and, consequently, that he never 
shines vertically on the same places for two days in succession. 
This may, perhaps, be providentially ordered, to prevent the too 
great effect of the Sun's heat, which, on the supposition that it 
is in inverse proportion to the square of the distance, is twice as 
great on this planet as it is on the Earth. 

3 76. At each pole of Yenus, the Sun continues half of her 
year without setting in summer, and as long without rising in 
winter ; consequently, her polar inhabitants, like those of the 
Earth, have only one day and one night in the year ; with this 
difference, that the polar days and nights of Yenus are not quite 
two-thirds as long as ours. 

Between her polar circles, which are but 15° from her equator, 
there are two winters, two summers, two springs, and two 
autumns, every year. But because the Sun stays for some time 
near the tropics, and passes so quickly over the equator, the win- 
ters in that zone will be almost twice as long as the summers. 

The north pole of Yenus' axis inclines towards the 20th 
degree of Aquarius ; the Earth's towards the beginning of Can- 
cer ; consequently, the northern parts of Yenus have summer 
in the signs where those of the Earth have winter, and vice versa. 

377. When viewed through a good telescope, Yenus exhibits 
not only all the moon-like phases of Mercury, but also a variety 
of inequalities on her surface ; dark spots, and brilliant shades, 
hills and valleys, and elevated mountains. But on account of 

375. What is the amount of the Sun's declination upon Venus ? What results ? What 
supposed design in this arrangement? 376. What said of the polar regions of Venus? 
What of her seasons ? How is her north pole situated with respect to the heavens ? 
What consequence? 377. How does Venus appear through a telescope? 



192 



ASTRONOMY. 



the great density of her atmosphere, these inequalities" are per- 
ceived with more difficulty than those upon the other planets. 




378. The mountains of Yenus, like those of Mercury and the 
Moon, are highest in the southern hemisphere. According to 
M. Schroeter, a celebrated German astronomer, who spent more 
than ten years in observations upon this planet, some of her 
mountains rise to the enormous height of from ten to twenty- 
two miles. The observations of Dr. Herschel do not indicate so 
great an altitude ; and he thinks, that in general they are con- 
siderably overrated. He estimates the diameter of Venus at 
8649 miles ; making her bulk more than one-sixth larger than 
that of the Earth. Several eminent astronomers affirm, that 
they have repeatedly seen Yenus attended by a satellite, and 
they have given circumstantial details of its size and appearance, 
its periodical revolution and its distance from her. It is said to 
resemble our Moon in its phases, its distance, and its magnitude. 
Other astronomers deny the existence of such a body, because 
it was not seen with Yenus on the Sun's disc, at the transits of 
1761 and 1769. 



THE EAKTH. 

379. The Earth is the place from which all our observations 
of the heavenly bodies must necessarily be made. The apparent 
motions of these bodies being very considerably affected by her 
figure, motions, and dimensions, these hold an important place in 
astronomical science. It will, therefore, be proper to consider, 
first, some of the methods by which they have been determined. 

If, standing on the sea-shore, in a clear day, we view a ship 
leaving the coast, in any direction, the hull or body of the vessel 

Why less distinct than the other planets ? 378. Where are her highest mountains 
situated? Their height? Remark of Dr. Herschel ? His estimate of Venus' diameter ? 
What said about a satellite around Venus? 379. Relation of the earth to the other 
planets in the study of astronomy? What necessary, therefore? What proof of the 
convexity of her surface ? 



THE PRIMARY PLANETS THE EARTH. 



193 



first disappears ; afterwards the rigging, and lastly the top of 
the mast vanishes from our sight. 



CONVEXITY OP THE EARTH'S SURFACE. 




Here the observer upon the shore at A sees only the topmasts of the ship, while the 
man standing upon the pillar at B sees the masts and sails, and part of the hull. Now, 
if the water between A and the ship were exactly flat instead of convex, the vision of A 
would extend along the line C, and he could see the whole ship as well as B. The advan- 
tage of B over A, in consequence of his elevation, shows that the surface of the water 
is convex between A and the ship. 

380. Again : navigators have sailed quite around the Earth, 
and thus proved its convexity. 

CONVEXITY 0? THE EARTH'S SURFACE. 

Ferdinand Magellan, a Portuguese, was the 
first who carried this enterprise into execution. 
He embarked from Seville, in Spain, and directed 
his course towards the west. After a long voy- 
age, he descried the continent of America. Not 
finding an opening to enable him to continue his 
course in a westerly direction, he sailed along the 
coast towards the south, till, coming to its south- 
ern extremity, he sailed around it, and found 
himself in the great Southern Ocean. He then 
resumed his course towards the west. After 
some time he arrived at the Molucca Islands, in 
the Eastern Hemisphere; and sailing con- 
tinually towards the west, he made Europe from 
the east, arriving at the place from which he 
set out.* 

The next who circumnavigated the Earth was 
Sir Francis Drake, who sailed from Plymouth, 
December 13, 1577, with five small vessels, and 
arrived at the same place, September 26, 15S0. 

Since that time, the circumnavigation of the Earth has been performed by Cavendish, 
Cordes, Noort, Sharten, Heremites, Dampier, Woodes, Rogers, Schovten, Roggewin, Lord 
Anson, Byron, Carteret, Wallis, Bougainville, Cook, King, Clerk, Vancouver, and many 
others. 

381. These navigators, by sailing in a westerly direction, 
allowance being made for promontories, &c, arrived at the coun- 
try they sailed from. Hence the Earth must be either cylindri- 
cal or globular. It cannot be cylindrical, because, if so, the 
meridian distances would all be equal to each other, which is 

* Magellan sailed from Seville, in Spain, August 10, 1519, in the ship called the Victory, 
accompanied by four other vessels. In April, 1521, he was killed in a skirmish with the 
natives,*at the island of Sebu, or Zebu, sometimes called Matan, one of the Philippines. 
One of his vessels, however, arrived at St. Lucar, near Seville, September 7, 1522. 

3S0. What second proof stated ? Who first sailed around the world? Who next? 
381. In what direction did they sail? How did these voyages prove the earth to be 




194 



ASTRONOMY. 



contrary to observation. The figure of the Earth is, therefore, 
spherical. 

382. The convexity of the Earth, north and south, is proved 
by the variation in the altitude of the pole, and of the circum- 
polar stars ; this is found uniformly to increase as we approach 
them, and to dimmish as we recede from them. 

LATITCDE FOUND BY THE NORTH STAR. 

Suppose an observer standing 
upon the Earth, and viewing the 
pole star from the 45° of North 
latitude ; it would, of course, 
appear elevated 46° above his 
visible horizon. But let him 
recede southward, and as he 
passed over a degree of latitude, 
the pole star would settle one 
degree towards the horizon, or 
more properly, his northern 
horizon would be elevated one 
degree towards the pole star, 
till at length, as he crossed the 
equator, the North star would 
sink below the horizon, and 
become invisible. Whence we 
derive the general rule, that 
the altitude of one pole, or the 
depression of the other, at any 
place on the Eartli's surface, is equal to the latitude of tliat place. 

383. The form of the Earth's shadow, as seen upon the Moon 
in an eclipse, indicates the globular figure of the Earth, and the 
consequent convexity of its surface. 

FORM OF THE EARTH'S SHADOW. 





spherical ? 382. What further proof have we that the earth is spherical? What rule 
based upon this phenomenon ? 383. What other evidence that the earth is a globe 
What remarks respecting the curvature of the earth's surface? What rules laid down 
based upon this curvature ? 



THE PRIMARY PLANETS THE EARTH. 



195 



Were the Earth a cube as shown at A, or in the form of a prism, as represented at B, 
her shadow would be more or less cubical or prismatic, as seen in the cut ; but instead 
of this, it is convex on all sides, as represented at C, plainly indicating the convexity of 
the Earth by which it is caused. 

The curvature of the Earth for one mile is 8 inches ; and this curvature increases with 
the square of the distance. From this general law it will be easy to calculate the distance 
at which any object whose height is given, may be seen, or to determine the height of an 
object when the distance is known. 

1st. To find the height of the object when the distance is given. 

Rule. Find the square of the distance in miles, and take two-thirds of that number 
for the height in feet. 

Ex. 1. — How high must the eye of an observer be raised, to see the surface of the 
ocean at the distance of three miles? Ans. The square of 3 ft. is 9 ft., and % of 9 ft. is 
6 ft. Ex. 2. — Suppose a person can just see the top of a spire over an extended plain of 
ten miles, how high is the steeple? Ans. The square of 10 is 100, and % of 100 is 
66 % feet.' 

2. To find the distance when the height is given. 

Rule. Increase the height in feet one-half, and extract the square root, for the dis- 
tance in miles. 

Ex. 1.— How far can a person seethe surface of a plain, whose eye is elevated six 
feet above it ? Ans. 6, increased by half, is 9, and the square root of S I is 3 : the distance 
is then 3 miles. Ex. 2. — To what distance can a person see a lighthouse whose height 
is 96 feet from the level of the ocean ? Ans. 96 increased by its half, is 144, and the 
square root of 144, is 12 ; the distance is therefore 12 miles. 

3. To find the curvature of the Earth when it exceeds a mile. 
Rule. Multiply the square of the distance by .000126. 

384. Although it appears from the preceding facts, that the 
Earth is spherical, yet it is not a perfect sphere. If it were, the 
length of the degrees of latitude, from the equator to the poles, 
would be uniformly the same ; but it has been found, by the 
most careful measurement, that as we go from the equator 
towards the poles, the length increases with the latitude. 

These measurements have been made by the most eminent mathematicians of different 
countries, and in various places, from the equator to the arctic circle. They have found 
that a degree of latitude at the arctic circle was nine- sixteenths of a mile longer than a 
degree at the equator, and that the ratio of increase for the intermediate degrees was 
nearly as the squares of the sines of the latitude. Thus the theory of Sir Isaac Newton 
was confirmed, that the body of the Earth was more rounded and convex between the 
tropics, but considerably flattened towards the poles. 



Places of 
Observation. 


Latitude. 


Length of a degree in 
English miles. 


Observers. 


Peru 

Pennsylvania 

Italy 

France 

England 

Sweden 


Equator. 
39° 12' N. 
43 01 
46 

51 29 54" 
66 20 10 


6S.732 
6S.896 
68.998 
69.054 
69.146 
69.292 


Bouguer, 

Mason and Dixon, 

Boscovich and Lemaire, 

Delambre and Mechain, 

Mudge, 

Swamberg. 



385. These measurements prove the Earth to be an oblate 
spheroid, whose longest or equatorial diameter is 19 24 miles, and 
polar diameter, 7898 miles. The mean diameter is, therefore, 
about 7912, and their difference 26 miles. The French Acade- 



384. But is the earth a sphere? What proof to the contrary? 885. What, then, is 
the earth's real figure ? What difference in her polar and equatorial diameters ? What 
demonstration that the earth is not an exact sphere ? 

B.G 9 




196 ASTRONOMY. 

my have determined that the mean diameter of the Earth, from 
the 4-5th degree of north latitude, to the opposite degree of 
south latitude, is accurately 7912 miles. 

If the Earth were an exact sphere, its diameter might be 
determined by its curvature, from a single measurement. Thus, 
in the adjoining figure, we have A B equal to 1 mile, and B D* 
equal to 8 inches, to find A E, or B E, which does not sensibly 
differ from A E, since B D is only 8 inches. Now it is a propo- 
sition of Euclid (B. 3, prop. 36), that, when from a point with- 
out a circle, two lines be drawn, one cutting and the other 
touching it, the touching line (B A) is a mean proportional be- 
tween the cutting line (B E) and that part of it (B D) without 
the circle. 

BD: BA: : BEorAE very nearly. 
That is, 1 mile being equal to 63,360 inches, 

8: 43,360 : : 63,360 : 50,181,120 inches, or 7920 miles. 
This is very nearly what the most elaborate calculations make the Earth's equatorial 
diameter. 

386. The Earth, considered as a planet, occupies a favored 
rank in the Solar System. It pleased the All-wise Creator to 
assign its position among the heavenly bodies, where nearly all 
the sister planets are visible to the naked eye. It is situated 
next to Yenus, and is the third planet from the Sun. 

To the scholar who for the first time takes up a book on astronomy, it will no doubt 
seem strange to find the Earth classed with the heavenly bodies. For what can appear 
more unlike, than the Earth, with her vast and seemingly immeasurable extent, and the 
stars, which appear but as points? The Earth is dark and opaque, the celestial bodies- 
are brilliant. We perceive in it no motion ; while in them we observe a continual change 
of place, as we view them at different hours of the day or night, or at different seasons' 
of the year. 

38 7. It moves round the Sun from west to east, in 365 days, 
5 hours, 48 minutes, and 48 seconds ; and turns the same way, 
on its axis, in 23 hours, 56 minutes, and 4 seconds. The former 
is called its annual motion, and causes the vicissitudes of the 
seasons. The latter is called its diurnal motion, and produces 
the succession of day and night. 

The Earth's mean distance from the Sun is about 95,000,000 
of miles. It consequently moves in its orbit at the mean rate of 
68,000 miles an hour. Its equatorial diameter being 1924 miles, 
it turns on its axis at the rate of 1040 miles an hour. 

Thus, the Earth on which we stand, and which has served for ages as the unshaken 
foundation of the firmest structures, is every moment turning swiftly on its center, and, 
at the same time, moving onwards with great rapidity through the empty space. 

This compound motion is to be understood of the whale Earth, with all that it holds 
within its substance, or sustains upon its surface — of the solid mass beneath, of the 
ocean which flows around it, of the air that rests upon it, and of the cloud's which float 
above it in the air. 

386. What said of the position of the earth in the system ? What remark as to classi- 
fying the earth as a planet? 387. State the time of the earth's revolution around the 
Sun ? On her own axis ? What are they called, respectively ? What is the earth's 
mean distance from the sun? Its mean rate of motion in its orbit? Hourly motion of 
bodies at the equator ? What twofold motion there ? Includes what ? 



THE PRIMARY PLANETS THE EARTH. 197 

388. That the Earth, in common with all the planets, revolves 
around the Sun as a center, is a fact which rests upon the clear- 
est demonstrations of philosophy. That it revolves, like them, 
upon its own axis, is a truth which every rising and setting sun 
illustrates, and which very many phenomena concur to establish. 
Either the Earth moves around its axis every day, or the whole 
universe moves around it in the same time. There is no third 
opinion that can be formed on this point. Either the Earth 
must revolve on its axis every twenty-four hours, to produce the 
alternate succession of day and night, or the Sun, Moon, planets, 
comets, fixed stars, and the whole frame of the universe itself, 
must move around the Earth, in the same time. 

389. To suppose the latter case to be the fact, would be to 
cast a reflection on the wisdom of the Supreme Architect, whose 
laws are universal harmony. As well might the beetle, that in 
a moment turns on its ball, imagine the heavens and the earth 
had made a revolution in the same instant. It is evident, that 
in proportion to the distance of the celestial bodies from the 
Earth, must, on this supposition, be the rapidity of their move- 
ments. The Sun, then, would move at the rate of more than 
400,000 miles in a minute ; the nearest stars, at the inconceiv- 
able velocity of 1,400,000,000 of miles in a second; and the 
most distant luminaries, with a degree of swiftness which no 
numbers could express, and all this, to save the little globe we 
tread upon, from turning safely on its axis, once in twenty-four 
hours. 

390. The idea of the heavens revolving about the Earth, is 
encumbered with innumerable other difficulties. We will men- 
tion only one more. It is estimated on good authority, that 
there are visible, by means of glasses, no less than 100,000,000 
of stars, scattered at all possible distances in the heavens above, 
beneath, and around us. Now, is it in the least degree probable, 
that the velocities of all these bodies should be so regulated, 
that, though describing circles so very different in dimensions, 
they should complete their revolutions in exactly the same time? 
In short, there is no more reason to suppose that the heavens 
revolve around the Earth, than there is to suppose that they 
revolve around each of the other planets, separately, and at the 
same time ; since the same apparent revolution is common to 
them all, for they all appear to revolve upon their axis, in differ- 
ent periods. 

388. What two motions has the earth? What proof of her diurnal revolution ? 389. 
Why not suppose the heavens revolve around us ? 390. What further proof? 



198 ASTRONOMY. 

391. The rotation of the Earth determines the length of the 
day, and may be regarded as one of the most important ele- 
ments in astronomical science. It serves as an universal measure 
of time, and forms the standard of comparison for the revolu- 
tions of the celestial bodies, for all ages, past and to come. 
Theory and observation concur in proving, that among the innu- 
merable vicissitudes that prevail throughout creation, the period 
of the Earth's diurnal rotation is immutable. 



SOLAR AND SIDEREAL TIME. 

392. The Earth performs one complete revolution on its axis 
in 23 hours, 56 minutes, and 4.09 seconds, of solar time. This 
is called a sidereal day, because, in that time, the stars appear 
to complete one revolution around the Earth. 

But, as the Earth advances almost a degree eastward in its 
orbit, in the time that it turns eastward around its axis, it is 
plain that just one rotation never brings the same meridian 
around from the Sun to the Sun again ; so that the Earth 
requires as much more than one complete revolution on its axis 
to complete a solar day, as it has gone forward in that time. 

SOLAR AND SIDEREAL TIME. 

j. q, SIDEREAL D^Y 

SOLAR DKY 



7% SUN ON THE MELRIDlAN 




To the man at A the Sun (S) is exactly on the meridian, or it is twelve o'clock, noon. 
The Earth passes on from B to D, and at the same time revolves on her axis. When she 
reaches D, the man who has stood on the same meridian has made a complete revolution, 
as determined by the star G (which was also on his meridian at twelve o'clock the day 
before) ; but the Sun is now east of the meridian, and he must wait/ow minutes for the 
Earth to roll a little further eastward, and bring the Sun again over his north and south 
line. If the Earth was not revolving around the Sun, her solar and sidereal days would 
be the same ; but as it is, she has to perform a little more than one complete revolution 
each solar day, to bring the Sun on the meridian. 

393. It is obvious, therefore, that in every natural or solar 
day, the Earth performs one complete revolution on its axis, and 
the 365th part of another revolution. Consequently, in 365 
days, the Earth turns 366 times around its axis. And as every 

391. What relation has the earth's diurnal revolution to time f What said of its regu- 
larity * 892. What is the time required for a complete revolution ? Explain the differ- 
ence between solar and sidereal time ? 393. Is a solar day more than a complete 
revolution of the earth on her axis? To what does this excess amount in a year? 



THE PRIMARY PLANETS THE EARTH. 199 

revolution of the earth on its axis completes a sidereal day, 
there must be 366 sidereal days in a year. And, generally, 
since the rotation of any planet about its axis is the length of a 
sidereal day at that planet, the number of sidereal days will 
always exceed the number of solar days by one, let that number 
be what it may, one revolution being always lost in the course 
of an annual revolution. This difference between the sidereal 
ar.d solar days may be illustrated by referring to a watch or 
clock. When both hands set out together, at 12 o'clock for 
instance, the minute hand must travel more than a whole circle 
before it will overtake the hour hand, that is, before they will 
come into conjunction again. 

394. In the same manner, if a man travel around the Earth 
eastwardly, no matter in what time, he will reckon one day more, 
on his arrival at the place whence he set out, than they do who 
remain at rest ; while the man who travels around the Earth 
westwardly will have one day less. Erom which it is manifest, 
that if two persons start from the same place at the same time, 
but go in contrary directions, the one traveling eastward and 
the other westward, and each goes completely around the globe, 
although they should both arrive again at the very same hour 
at the same place from which they set out, yet they will disagree 
two whole days in their reckoning. Should the day of their 
return, to the man who traveled westwardly, be Monday, to 
the man who travelled eastwardly, it would be Wednesday ; 
while to those who remained at the place itself, it would be 
Tuesday. 

395. ]S"or is it necessary, in order to produce the gain or loss 
of a day, that the journey be performed either on the equator, 
or on any parallel of latitude : it is sufficient for the purpose, 
that all the meridians of the Earth be passed through, eastward 
or westward. The time, also, occupied in the journey, is equally 
unimportant ; the gain or loss of a day being the same, whether 
the Earth be traveled around in 24 years, or in as many hours. 

396. It is also evident, that if the Earth turned around its 
axis but once in a year, and if the revolution was performed the 
same way as its revolution around the Sun, there would be per- 
petual day on one side of it, and perpetual night on the other. 

Hence "what general rule? What illustration referred to? 394. What effect has tra- 
veling east or west, upon time ? Hence what result? 395. Is it important that the sup- 
posed journeys be performed in a short period? 396. How would it be if the Earth 
revolved on her axis but once a year ? 



200 ASTRONOMY. 

From these facts the pupil will readily comprehend the principles involved in a curious 
problem which appeared a few years ago. It was gravely reported by an American ship, 
that, in sailing over the ocean, it chanced to find six Sundays in February. The fact 
was insisted on, and a solution demanded. There is nothing absurd in this. The man 
who travels around the earth eastwardly, will see the Sun go down a little earlier every 
succeeding day, than if he had remained at rest; or earlier than they do who live at the 
place from which he set out. The faster he travels towards the rising sun, the sooner 
will it appear above the horizon in the morning, and so much sooner will it set in the 
evening. What he thus gains in time, will bear the same proportion to a solar day, as 
the distance traveled does to the circumference of the Earth. As the globe is 360 degrees 
in circumference, the Sun will appear to move over one twenty-fourth part of its surface, 
or 14° every hour, which is 4 minutes to one degree. Consequently, the Sun will rise, 
come to the meridian, and set, 4 minutes sooner, at a place 1° east of us, than it will 
with us; at the distance of 2° the Sun will rise and set 8 minutes sooner; at the distance 
of 3°, 12 minutes sooner, and so on. 

Now the man who travels one degree to the east, the first day will have the Sun on his 
meridian 4 minutes sooner than we do who are at rest ; and the second day 8 minutes 
sooner, and on the third day 12 minutes sooner, and so on ; each successive day being 
completed 4 minutes earlier than the preceding, until he arrives again at the place from 
which he started : when this continual gain of 4 minutes a day will have amounted to a 
whole day in advance of our time : he having seen the Sun rise and set once more than 
we have. Consequently, the day on which he arrives at home, whatever day of the 
week it may be, is one day in advance of ours, and he must needs live that day over 
again, by calling the next day by the same name, in order to make the accounts 
harmonize. 

If this should be the last day of February in a bissextile year, it would also be the 
same day of the week that the first was, and be six times repeated, and if it should 
happen on Sunday, he would, under these circumstances, have six Sundays in February. 

Again : whereas the man who travels at the rate of one degree to the east, will have 
all his days 4 minutes shorter than ours, so, on the contrary, the man who travels at the 
same rate towards the west, will have all his days 4 minutes longer than ours. When he 
has finished the circuit of the Earth, and arrived at the place from which he first set 
out, he will have seen the Sun rise and set once less than we have. Consequently, the 
day he gets home will be one day after the time at that place; for which reason, if he 
arrives at home on Saturday, according to his own account, he will have to call the next 
day Monday ; Sunday having gone by before he reached home. Thus, on whatever day 
of the week January should end, in common years, he would find the same day repeated 
only three times in February. If January ended on Sunday, he would, under these cir- 
cumstances, find only three Sundays in February. 

39 T. The Earth's motion about its axis being perfectly equable 
and uniform in every part of its annual revolution, the sidereal 
days are always of the same length, but the solar or natural days 
vary very considerably at different times of the year. This varia- 
tion is owing to two distinct causes, the inclination of the Earth's 
axis to its orbit, and the inequality of its motion around the Sun. 
From these two causes it is, that the time shown by a well-regu- 
lated clock and that of a true sun-dial are scarcely ever the 
same. The difference between them, which sometimes amounts 
to 16^ minutes, is called the Equation of Time, or the equation 
of solar days. 

What curious facts accounted for ? What supposition of a man traveling eastward 
one degree a day? What effect upon the time of the Sun's passing the meridian? Upon 
the length of his day? What change of name may it require? 397. Are the solar 
and sidereal days alike uniform as to length ? Why do solar days vary in length? Why 
do not a dial and clock agree ? What is the Equation of Time ? 



THE PRIMARY PLANETS THE EARTH. 



201 




EQUATION OF 

The difference between 
mean and apparent time, 
or, in other words, between 
Equinoctial and Ecliptic 
time, may be further shown 
by this figure, which repre- 
sents the circles of the 
sphere Let it be first pre- 
mised, that equinoctial time 
is clock tame ; and that 
ecliptic time is solar or 
apparent time. It appears 
that from Aries to Cancer., 
the Sun in the ecliptic comes 
to the meridian before the 
equinoctial Sun ; from Can- 
cer to Libra, after it; from 
Libra to Capricorn before 
it; and from Capricorn to 
Aries after it. If we notice 
what months the Sun is in 
these several quarters, we 
shall find that from the 25th 
of December to the 16th of 
April, and from the 16th of 
June to the 1st of Septem- 
ber, the clock is- faster than 
the sun-dial ; and that, from 

the 16th of April to the 16th of June, and from the 1st of September to the 25th of Dec, 
the sun-dial is faster than the clock. 

398. It is an universal fact, that, while none of the planets are 
perfect spheres, none of their orbits are perfect circles. The 
planets all revolve about the Sun, in ellipses of different degrees 
of eccentricity ; having the Sun, not in the center of the ellipse, 
but in one of its foci. 

The figure A D B E is an ellipse. The line A B is 
called the transverse axis, and the line drawn through 
the middle of this line, and perpendicular to it, is the 
conjugate axis. The point C, the middle of the trans- 
verse axis, is the center of the ellipse. The points 
F and f, equally distant from C, are called the foci. 
C F, the distance from the center to one of the- foci, 
is called the eccentricity. The orbits of the planets 
being ellipses, having the Sun in one of the foci, if 
A D B E be the orbit of a planet, with the Sun in the 
focus F, when the planet is at the point A, it will be in 
its perihelion, or nearest the Sun ; and when at the 
point B in its aphelion, or at its greatest distance 
from the Sun. The difference in these distances is 
evidently equal to F f, that is, equal to twice the eccentricity of its orbit. In every revo- 
lution, a planet passes through its perihelion and aphelion. The eccentricity of the 
Earth's orbit is about one and a half millions of miles ; hence she is 3,000,000 of miles, 
nearer the Sun in her perihelion, than in her aphelion. 

Hvow as the Sun remains fixed in the lower focus of the Earth's orbit, it is easy to per- 
ceive that a line, passing centrally through the Sun at right angles with the longer axis 
of the orbit, will divide it into two unequal segments. Precisely thus it is divided by 
the equinoctial. 

399. That portion of the Earth's orbit which lies above the 




398. What is the true form of the planets' orbits ? Why is equinoctial time irregular? 
J9. How is the Earth's orbit divided by the equinoctial? 



h. 


m. 


d. 


h. m. 


21 
14 


19) 
1 f 


183 


11 19 


IT 
1 


IT i 

13] 


1T8 


18 30 



202 ASTRONOMY. 

Sun, or north of the equinoctial, contains about 184 degrees , 
while that portion of it which lies below the Sun, or south of the 
equinoctial, contains only 1^6 degrees. This fact shows why 
the Sun continues about eight days longer on the north side of 
the equator in summer, than it does on the south side in winter. 
The exact calculation, for the year 1830, is as follows : 

d. 
From the vernal equinox to the summer solstice, = 92 

From the summer solstice to the autumnal equinox, = 93 

From the autumnal equinox to the winter solstice, = 89 

From the winter solstice to the vernal equinox, = 89 

Difference in favor of the north side, = 7 16 49 

The points of the Earth's orbit which correspond to its greatest and least distances 

from the Sun, are called, the former the Apogee, and the latter the Perigee; two Greek 

words, the former of which signifies from the Earth, and the latter about the Earth. 

These points are also designated by the common name of Apsides. 

400. The Earth being in its perihelion about the 1st of Jan- 
uary, and in its aphelion the 1st of July, we are 3,000,000 of 
miles nearer the Sun in winter than in midsummer. The reason 
why we have not, as might be expected, the hottest weather 
when the Earth is nearest the Sun, is, because the Sun, at that 
time, having retreated to the southern tropic, shines so obliquely 
on the northern hemisphere, that its rays have scarcely half the 
effect of the summer Sun ; and continuing but a short time above 
the horizon, less heat is accumulated by day than is dissipated 
by night. 

401. As the Earth performs its annual revolution around the 
Sun, the position of its axis remains invariably the same ; always 
pointing to the North Pole of the heavens, and always main- 
taining the same inclination to its orbit. This seems to be pro- 
videntially ordered for the benefit of mankind. If the axis of 
the Earth always pointed to the center of its orbit, all external 
objects would appear to whirl about our heads in an inexplicable 
maze. Nothing would appear permanent. The mariner could 
no longer direct his course by the stars, and every index in 
nature would mislead us. 

What phenomenon does this explain? 400. When is the Earth in its perihelion? Its 
aphelion? What difference in its distance from the Sun? Why, then, have we not the 
warmest weather in January? 401. What said of the permanency of the Earth's axis? 
How would it be if either pole was toward the Sun ? 



THE MOON HER DISTANCE, MOTIONS, PHASES. 



203 



CHAPTER IV. 

THE MOON— HEE DISTANCE, MOTIONS, PHASES, &o. 

402. There is no object within the scope of astronomical 
observation which affords greater variety of interesting investi- 
gation than the various phases and motions of the Moon. Prom 
them the astronomer ascertains the form of the Earth, the vicis- 
situdes of the tides, the causes of eclipses and occultations, the 
distance of the Sun, and, consequently, the magnitude of the 
solar system. These phenomena, which are perfectly obvious to 
the unassisted eye, served as a standard of measurement to all 
nations, until the advancement of science taught them the advan- 
tages of solar time. It is to these phenomena that the naviga- 
tor is indebted for that precision of knowledge which guides him 
with well-grounded confidence through the pathless ocean. 

The Hebrews, the Greeks, the Romans, and, in general, all 
the ancients, used to assemble at the time of new or full Moon, 
to discharge the duties of piety and gratitude for her unwearied 
attendance on the Earth, and all her manifold uses. 

The philosophy of the changes of the Moon is illustrated by 
the following cut : 

PHILOSOPHY OF THE MOON'S CHANGES. 



O*'-^. 

FIRST 08. ••. 

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[i "~\ \ *&ss£* 



„ x **\Cfi& 



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\ \ 

GiBBOOS^) 







' %>:"' 

4 \ 

This cut represents the moon revolving eastward around the Earth. In the outside 
circle, she is represented as she would appear, if viewed from a direction at right angles 
with the plane of her orbit. The side toward the Sun is enlightened in every case, and 
she appears like a half moon at every point. 

402. What said of the Moon's motions and phases ? What learned from them? How 
used anciently? How at the present time? How did the ancients observe the new and 
full moons ? 

9* 



204 ASTRONOMY. 

The interior suit represents her as she appears when viewed from the earth. At A it is 
New Moon ; and if seen at all so near the Sun, she would appear like a dark globe. At 
B she would appear like a crescent, concave toward the east. At C, more of her enlight- 
ened side is visible ; at D still more ; and at E the enlightened hemisphere is fully in 
view. We then call her a Full Moon. From E around to A again, the dark portion 
becomes more and more visible, as the luminous part goes out of view, till she comes to 
her change at A. When at D and F the moon is said to be gibbous. 

403. When the Moon, after having been in conjunction with 
the Sun, emerges from his rays, she first appears in the evening, 
a little after sunset, like a fine luminous crescent, with its convex 
side towards the Sun. If we observe her the next evening, we 
find her about 13° farther east of the Sun than on the preceding 
evening, and her crescent of light sensibly augmented. Repeat- 
ing these observations, we perceive that she departs farther and 
farther from the Sun, as her enlightened surface comes more and 
more into view, until she arrives at her first quarter, and comes 
to the meridian at sunset. She has then finished half her course 
from the new to the full, and half her enlightened hemisphere is 
turned towards the Earth. 

404. After her first quarter, she appears more and more gib- 
bous, as she recedes farther and farther from the Sun, until she 
has completed just half her revolution around the Earth, and is 
seen rising in the east when the Sun is setting in the west. She 
then presents her enlightened orb full to our view, and is said 
to be in opposition ; because she is then on the opposite side of 
the Earth with respect to the Sun. 

In the first half of her orbit she appears to pass over our 
heads through the upper hemisphere ; she now descends below 
the eastern horizon to pass through that part of her orbit which 
lies in the lower hemisphere. 

405. After her full she wanes through the same changes of 
pearance as before, but in an inverted order ; and we see her in 
the morning like a fine thread of light, a little west of the rising 
Sun. For the next two or three days she is lost to our view, 
rising and setting in conjunction with the Sun ; after which, she 
passes over, by reason of her daily motion, to the east side of 
the Sun, and we behold her again, a new Moon, as before. In 
changing sides with the Sun, she changes also the direction of 
her crescent. Before her conjunction it was turned to the east ; 
it is now turned towards the west. These different appearances 
of the Moon are called her phases. They prove that she shines 



403. Explain the cause of the changes of the Moon ? 404. How after her first quarter? 
405. How after her full? What change in her crescent? What do the Moon's phases 
prove ? 



THE MOON HER MOTIONS, PHASES, ETC. 205 

not by any light of her own ; if she did, being globular, we 
should always see her a round full orb like the Sun. 

406. The Moon is a satellite to the Earth, about which she 
revolves in an elliptical orbit, in 29 days, 12 hours. 44 minutes, 
and 3 seconds ; the time which elapses between one new moon 
and another. This is called her synodic revolution. Her revo- 
lution from any fixed star to the same star again, is called her 
periodic or sidereal revolution. It is accomplished in 21 days, 1 
hours, 43 minutes, and ll-§- seconds ; but in this time, the Earth 
has advanced nearly as many degrees in her orbit ; consequently, 
the Moon, at the end of one complete revolution, must go as 
many degrees farther, before she will come again into the same 
position with respect to the Sun and the Earth. 

SIDEBEAL AND SYNODIC REVOLUTIONS OP THE MOON. 

'-s\ — X 

£ w ?IP.! : ^.^..?i!yo^IiP.N„a7^DAYg. i . , .. . B i^ /fSSk E ; 



»9*°#?. " C 

: 



" f! . L; / 



^&-" : - Vju/ 



SUN AND MOON IN C0NJUN0TI0N-MEW MOON,'" 

IT 



On the right, the earth is shown in her orbit, revolving around the sun, and the moon 
in her orbit, revolving around the earth. At A, the sun and moon are in conjunction, 
or it is New Moon. As the earth passes from D to E, the moon passes around from A to 
B, or the exact point in her orbit where she was 27% days before. But she is still west 
of the sun, and must pass on from B to C, or 1 day and 20 hours longer, before she can 
again come in conjunction with him. This 1 day and 20 hours constitutes the difference 
between a sidereal and a synodic revolution. 

The student will perceive that the difference between a sidereal and synodic revolution 
of the moon, like that between solar and sidereal time, is due to the same cause, namely, 
the revolution of the earth around the sun. 

401. Lying along the Moon's path, there are nine conspicu- 
ous stars that are used by nautical mem for determining their 
longitude at sea, thence called nautical stars. These stars are, 
Arietes, Aldebaran, Pollux, Regulus, Spica Virginis, Antares, 
Alt aire, Fomalkaut, and Markab. 

The true places of these stars, for every day in the year, are given in the Nautical 
Almanac, a valuable work published annually by the English " Board of Admiralty," to 
guide mariners in navigating the seas. They are usually published two or three years in 
advance, for the benefit of long voyages. 

Let A in the cut represent Greenwich Observatory, near London. B is the Moon, and 
C her apparent pi ace among the distant stars, about 40° west of the star D. The ship E, 
having Greenwich time, as well as her own local time, sails from London westward ; 

406. Form of the lunar orbit ? Time of synodic revolution? Of sidereal revolution ? 
What difierence ? 407. What are the nautical stars? Can you explain how longitude 
is ascertained by them? 



206 



ASTRONOMY 



but on observing the Moon when, by Greenwich 
time, she ought to be at C, she is found to be at F, or 
only about 20° west of the star D. It is, therefore, 
obvious that the ship is west of Greenwich, as the 
Moon appears east of her Greenwich place. From 
this difference between her place as laid down in the 
tables, and her observed place, as referred to cer- 
tain prominent stars, the mariner determines how 
far he is east or west of the meridian of Greenwich. 
The Moon's geocentric place (or place as viewed 
from the center of the Earth) may be given instead 
of her Greenwich place, and the same conclusions 
arrived at. In either case, this is called the lunar 
method of determining the longitude. It is also ascer- 
tained by simple comparison of local and standard 
time, that a man, says Sir John Herschel, by merely 
measuring the Moon's apparent distance from a star, 
with a little portable instrument held in his hand, 
and applied to his eye, even with so unstable a foot- 
ing as the deck of a ship, shall say positively within 
five miles where he is, on a boundless ocean, cannot 
but appear to persons ignorant of physical astronomy 
an approach to the miraculous. And yet, says he, 
the alternatives of life and death, wealth and ruin, 
are daily and hourly staked, with perfect confidence, 
on these marvellous computations. 

408. The Moon is the nearest of all the heavenly bodies, being 
about thirty times the diameter of the Earth, or 240,000 miles, 
distant from us. Her mean daily motion in her orbit is nearly 
fourteen times as great as the Earth's ; since she not only accom- 
panies the Earth around the Sun every year, but, in the mean 
time, performs nearly thirteen revolutions about the Earth. 

Although the apparent motion of the Moon in her orbit is greater than that of any 
other heavenly body, since she passes over, at a mean rate, no less than 13° 10' 35" in a 
day ; yet this is to be understood as angular motion, — motion in a small orbit — and 
therefore embracing a great number of degrees, and but comparatively few miles. 




\ 



©-. 



---©- 



409. The point in the Moon's orbit 
nearest the Earth is called Perigee, from 
\ the Greek peri, about, and ge, the earth. 
\ The point most distant is called Apogee, 
from apo, from, and ge, the earth. These 
two points are also called the apsides 
of her orbit ; and a line joining them, 
the line of the apsides. 

See the Moon in apogee and perigee in the cut. The 
singular of apsides is apsis. 

y' 410. The line of the apsides of the 

Moon's orbit is not fixed in the ecliptic, 
but revolves slowly around the ecliptic, 



408. The Moon's distance? Daily motion in orbit? How many degrees? 409. 
Perigee and Apogee ? Derivation? What other name for these two points? What is 
the line of the apsides? 410. la this line stationary? What motion? Its period of 
revolution ? 



dr* O 




\ F 


a :// 


C&5 Gt 


,0 



THE MOON HER MOTIONS, PHASES, ETC. 207 

from west to east, in the period M0TI0N 0F THE apsides. 

of about nine years. J^&r. 

In the adjoining cut, an attempt is made to .—»-••""* * -'' *'\-r— -. 

represent this motion. At A, the line of the Cjfyf C ■J-^^-y' 

apsides points directly to the right and left; ""v^T--' D B * "<■ 

but at B, C, and D, it is seen changing its 
direction, till at E the change is very percep- 
tible when compared with A. But the same 
ratio of change continues ; and at the end of 
a year, when the Earth reaches A again, the 
line of the apsides is found to have revolved 
eastward to the dotted line I K, or about 40°. 
In nine years the aphelion point near A will 
have made a complete revolution, and return- 
ed i.o its original position. 

411. The line of the Moon's 
nodes is also in revolution ; but 
it retrogrades or falls back westward, making the circuit of the 
ecliptic once in about nineteen years. 

4 1 2. Though her orbit is an ellipse, b ^. ,<,.*?.,---*. 
with respect to the Earth, it is, in 
reality, an irregular curve, always 
concave toward the Sun, and crossing 
the Earth's orbit every 13° nearly. 4f^~ Wy "#? 

If the Earth stood still in her orbit, the Moon \.l-, fTjl ...:.--'' 

would describe just such a path in the ecliptic as /T '^k& "i\ 

she describes with respect to the Earth. i ^ (§i ) 

If the Earth moved but slowly on her way, the *\ \ , m •-. . * 

Moon would actually retrograde on the ecliptic at *S"C ''&"' 

the time of her change, and would cross her own •. "^ , # # @H& } 

path at every revolution, as shown in the adjoin- V^5& 6 ^, .: ~ :}:" ;•' 

ing figure. But as the Earth advances some \'W-ii-^'/ ' 

46,000,000 of miles, or near 100 times the diameter **••.*■" '~^.+ ' 

of the Moon's orbit, during a single lunation, it is 

evident that the Moon's orbit never can return into itself, or retrograde, a3 here repre- 
sented. 

That the lunar orbit is always concave toward the Sun, may be demonstrated bv the 
above diagram. 

THE MOON'S ORBIT ALWAYS CONCAVE TOWARD THE SUN. 



C 



™«£i th,S h /7% hn ?A B ™V v i sent an arc of the Earth's orbit, equal to that 
known Sf/f.f' 11 ,' 1 ? 8 half a Nation. Now the radius -and arc being 
^?.7h ' V* ^ 4 hat ^ 6 Ch ° rd A B must P ass more thaQ 4 ^0,000 miles within thl 
?nnni; tw *£ e M .°°? de ?^te only 240,000 from the Earth, as shown in the figure, it 
toward the Sun describe the curve denoted by the middle line, which is concave 

This subject may be still further illustrated by the following cut : 

m™ 1 * H0W -^ ith J he *?%? 4 he ^ Ioon ' s nodes? 412 - mat is the actual form of the 
Moons orbit? How if the Earth stood still? How if she moved but slowly? How is 
.he Moon's orbit demonstrated to be always concave towards the Sun ? 



208 



ASTRONOMY. 



THE MOON'S PATH DURING A COMPLETE LUNATION. 




Here the plain line represents the Earth's orbit, and the dotted one that of the Moon. At 
A the Moon crosses the Earth's track 240,000 miles behind her. She gains on the Earth, 
till in seven days she passes her at B as a Full Moon. Continuing to gain on the Earth, 
she crosses her orbit at C, 240,000 miles ahead of her, being then at her Third Quarter. 
From this point the Earth gains upon the Moon, till seven days afterward she overtakes 
her at D as a New Moon. From D to E the Earth continues to gain, till at E the Moon 
crosses 240,000 behind the Earth, as she had done four weeks before at A. Thus the 
Moon winds her way along, first within and then without the Earth ; always gaining upon 
us when outside of our orbit, and falling behind us when within it. 

The small circles in the cut represent the Moon's orbit with respect to the Earth, which 
is as regular to us as if the Earth had no revolution around the Sun. 

413. The moon never retrogrades on the ecliptic, or returns 
into her own path again ; but is always advancing with the 
Earth, at the rate of not less than 65,700 miles per hour. 

moon's path. The Moon's orbitual velocity, with respect to the 

Earth, is about 2800 miles per hour. When outside 
the Earth, as at B, in the last figure, she gains 2300 
miles per hour, which added to the Earth's velocity, 
would give 70,300 miles as the hourly velocity of the 
Moon. When within the Earth's orbit, as at D, she 
loses 2300 miles per hour, which, substracted from 
68,000 miles (the Earth's hourly velocity), would leave 
65,700 miles as the slowest motion of the Moon in 
space, even when she is falling behind the Earth. 

Could we look down perpendicularly upon the eclip- 
tic, and see the paths of the Earth and Moon, we should 
see the latter pursuing her serpentine course, first 
within and then outside our globe, somewhat as repre- 
sented by the dotted line in the annexed figure. Her 
path, however, would be concave toward the Sun, as 
shown on the preceding page, and not convex, as we 
were obliged to represent it here in so small a diagram. 

414. In her journeyings eastward, the Moon often seems to 
run over and obscure the distant planets 
and stars. This phenomenon is called 
an occultation. 

The adjoining cut represents the new Moon as just 
about to obscure a distant star, by passing between 
us and it. In 1850, she occulted Jupiter for three 
revolutions in succession — viz., Jan. 30th, Feb. 27th, 
and March 26th. Through a telescope, the Moon is 
seen to be constantly obscuring stars that are invisi 
ble to the naked eye. They disappear behind the 
Moon's eastern limb, and in a short time reappear 
from behind her western ; thus distinctly exhibiting 
her eastward motion. 



413. Does she ever retrograde on the ecliptic? What is her slowest motion? How 
demonstrated ? 414. What- is an occultation ? Remarks respecting this phenomenon? 





THE MOON HER MOTIONS, PHASES, ETC. 



209 



MOON'S REVOLUTION. 



fa 



V 



'*) 



415. Tho Moon revolves once on her axis exactly in the time 
that she performs her revolution around the Earth. This is evi- 
dent from her always presenting the same side to the Earth ; 
for if she had no rotation upon an axis, every part of her surface 
would be presented to a spectator on the Earth, in the course 
of her sy nodical revolution. It fol- 
lows, then, that there is but one day 
and night in her year, containing, 
both together, 29 days, 12 hours, 
44 minutes, and 3 seconds. 

Suppose a monument erected upon the Moon's 
surface, so as to point toward the Earth at New 
Moon, as represented at A. From the Earth it 
would appear in the Moon's center. Now if the 
Moon so revolve upon her axis, in the direction of 
the arrows, as to keep the pillar pointing directly 
toward the Earth, as shown at A, B, C, and D, and 
the intermediate points, she must make just one 
revolution on her axis during her periodic revolu- 
tion. At A, the pillar points from, the Sun, and at 
C toward him : showing that, in going half-way 
round the Earth, she has performed half a revolu- 
tion upon her axis. 

416. Though the Moon always presents nearly the same hemi- 
sphere toward the Earth, it is not always precisely the same. 
Owing to the ellipticity of her orbit, and the consequent 
inequality of her angular velocity, she appears to roll a little on 
her axis, first one way and then the other — thus alternately 
revealing and hiding new territory, 
as it were, on her eastern and west- 
ern limbs. This rolling motion east 
and west is called her Vibration in 
longitude. 



tr^ 



*) 



MOON'S LTBKATION. 



Cl 



"-V 



C 






% 



4) 



^ 



*fc 



» 



The accompanying cut will illustrate the subject 
of the Moon's Orations in longitude. 

From A around to C, the angular motion is 
slower than the average, and the diurnal motion 
gains upon it, t>o that the pillar points west of the 
Earth, and we see more of the eastern limb of the 
moon. 

From C to A, again, the Moon advances/asfer 
than a mean rate, and gains upon the diurnal 
revolution; so that the pillar points east of the 
Earth, and we see more of the Moon's western 
limb. Thus she seems to librate or roll, first 
one way and then the other, during every periodic 
revolution. 

At B, we see most of her eastern limb ; and at D, most of her western. 

41 T. The axis of the Moon is inclined to the plane of her 
orbit only about one and a half degrees (1° 30' 10.8"). But this 

415. How often does the Moon revolve on her axis? How is it known ? What follows 
from this fact? 416. What are the Moon's Iterations? In Longitude? 417. In 
Latitude t 



210 ASTRONOMY. 

slight inclination enables us to see first one pole and then the 
other, in her revolution around the Earth. These slight rolling 
motions are called her lib-rations in latitude. 

As tne inclination of the Earth's axis brings first one pole and then the other toward the 
Sun, and produces the seasons, so the inclination of the Moon's axis brings first one pole 
and then the other in view from the Earth. But as her inclination is only 1%°, the 
libration in latitude is very slight. 

418. As the Moon turns on her axis only as she moves around 
the Earth, it is plain that the inhabitants of one half of the 
lunar world are totally deprived of the sight of the Earth, unless 
they travel to -the opposite hemisphere. This we may presume 
they will do, were it only to view so sublime a spectacle ; for it 
is certain that from the Moon the Earth appears ten times larger 
than any other body in the universe. 

419. As the Moon enlightens the Earth, by reflecting the light 
of the Sun, so likewise the Earth illuminates the Moon, exhibit- 
ing to her the same phases that she does to us, only in a con- 
trary order. And, as the surface of the Earth is 13 times as 
large as the surface of the Moon, the Earth, when full to the 
Moon, will appear 13 times as large as the full Moon does to us. 
That side of the Moon, therefore, which is towards the Earth, 
may be said to have no darkness at all, the Earth constantly 
shining upon it with extraordinary splendor when the Sun is 
absent ; it therefore enjoys successively two weeks of illumina- 
tion from the Sun, and two weeks of earth-light from the Earth. 
The other side of the Moon has alternately a fortnight's light, 
and a fortnight's darkness. 

420. As the Earth revolves on its axis, the several continents, 
seas, and islands, appear to the lunar inhabitants like so many 
spots of different forms and brightness, alternately moving over 
its surface, being more or less brilliant, as they are seen through 
intervening clouds. By these spots, the lunarians can not only 
determine the period of the Earth's rotation, just as we do that 
of the Sun, but they may also find the longitude of their places, 
as we find the latitude of ours. 

421. As the full Moon always happens when the Moon is 
directly opposite the Sun, all the full moons in our winter, must 
happen when the Moon is on the north side of the equinoctial, 

418. Can all the Lunarians see the Earth? How large must she appear from the 
Moon? 419. What said of her light and phases ? How, then, are the two hemispheres of 
the Moon enlightened? 420. How must the Earth appear to the Lunarians, and what 
may they infer from the motion of the spots seen on her surface? 421. Where is the 
Moon at the full in winter? In summer? Why? What result as to moonlight at the 
poles ? 



THE MOON HER MOTIONS, PHASES, ETC. 211 

because then the Sun is on the south side of it ; consequently, at 
the north pole of the Earth, there will be a fortnight's moon- 
light and a fortnight's darkness by turns, for a period of six 
months, and the same will be the fact during the Sun's absence 
the other six months, at the south pole. 

422. The plane of the Moon's orbit is very near that of the 
ecliptic. It departs from the latter only about 5-J° (5° 8' 48'"'.) 

INCLINATION OF THE MOON'S ORBIT TO THE PLANE OF THE ECLIPTIC. 




Let the line A B represent the plane of the Earth's orbit, and the line joining the Moon 
at C and D would represent the inclination of the Moon's orbit to that of the Earth. At 
C the Moon would be within the Earth's orbit, and at D exterior to it ; and it would be 
Full Moon at D, and New Moon at C 

423. The Moon's axis being inclined only about 1^-° to her 
orbit, she can have no sensible diversity of seasons ; from which 
we may infer, that her atmosphere is mild and uniform. The 
quantity of light which we derive from the Moon when full, is at 
least 300,000 times less than that of the Sun. 

This is Monsieur Bouquer's inference, from his experiments, as stated by La Place, in 
his work, p. 42. The result of Dr. Wollaston's computations was different. Professor 
Leslie makes the light of the Moon 150,000 times less than that of the Sun ; it was for- 
merly reckoned 100,000 times less. i 

424. The Moon, though apparently as large as the Sun, is the 
smallest of all the heavenly bodies that are visible to the naked 
eye. Her diameter is but 2162 miles ; consequently her surface 
is 13 times less than that of the Earth, and her bulk 49 times 
less. It would require 70,000,000 of such bodies to equal the 
volume of the Sun. The reason why she appears as large as the 
Sun, when, in truth, she is so much less, is because she is 400 
times nearer to us than the Sun. 

425. When viewed through a good telescope, the Moon pre- 
sents a most wonderful and interesting aspect. Besides the 
large dark spots, which are visible to the naked eye, we perceive 
extensive valleys, shelving rocks, and long ridges of elevated 
mountains, projecting their shadows on the plains below. Single 
mountains occasionally rise to a great height, while circular hol- 
lows more than three miles deep, seem excavated in the plains. 

422. How is the Moon's orbit situated with respect to the ecliptic ? 423. What is 
the inclination of the Moon's axis, and what effect has it on her seasons and atmosphere ? 
What is the amount of light derived from the Moon as compared with the Sun, and is 
there any difference of opinion on this point? 424. What said of the apparent and 
real diameters of the Moon? Compared with the Earth? The Sun? Why, then, 
appear as large as he does? 425. How does she appear through a telescope? 



212 



ASTRONOMY. 




telescopic view of the moon. Specimens of these shadows may 

be seen in the cut, projecting to 
the left. Bright points of light, or, 
in other words, the illuminated 
tops of mountains, may also be 
seen near the terminator, in the 
dark portion. The writer has often 
watched them, and seen them en- 
large more and more, as the Sun 
arose upon the side of the Moon 
toward us, and enlightened the 
sides of her mountains. 

The shadows are always pro- 
jected in a direction opposite the 
Sun, or towards the dark side 
of the moon ; and as her eastern 
limb is dark from the change to the 
full, and her western from the full 
to the change, of course the direc- 
tion of the shadows must be re- 
versed. 

Suppose a person stationed at a 
distance directly over the Andes. 
Before the Sun arose, he would see 
the tallest peaks enlightened ; and 
as he arose, the long shadows of 
the mountains would extend to the 
west. At noon, however, little or no shadow would be visible ; but at sunset, they would 
again be seen stretching away to the east. This is precisely the change that is 
seen to take place with the lunar shadows, except that the time required is a lunar day, 
equal to about 15 of our days, instead of one of our days of 12 hours. 

426. The Moon's mountain scenery bears a striking resem- 
blance to the towering sublimity and terrific ruggedness of the 
Alpine regions, or of the Apennines, after which some of her 
mountains have been named, "and of the Cordilleras of our own 
continent. Huge masses of rock rising precipitously from the 
plains, lift their peaked summits to an immense height in the air, 
while shapeless crags hang over their projecting sides, and seem 
on the eve of being precipitated into the tremendous chasm 
below. 

Around the base of these frightful eminences, are strewed 
numerous loose and unconnected fragments, which time seems to 
have detached from their parent mass ; and when we examine 
the rents and ravines which accompany the overhanging cliffs, 
the beholder expects every moment that they are to be torn 
from their base, and that the process of destructive separation 
which he had only contemplated in its effects, is about to be 
exhibited before him in all its reality. 

42 T. The range of mountains called the Apennines, which 
traverses a portion of the Moon's disc from northeast to south- 
west, and of which some parts are visible to the naked eye, rises 



426. What said of the Moon's mountain scenery' 
ticular? 



427. Of the Apennines in par- 



THE MOON HER MOTIONS, PHASES, ETC. 213 

with a precipitous and craggy front from the level of the Mare 
Imbriwm, or Sea of Showers. In this extensive range are several 
ridges whose summits have a perpendicular elevation of four 
miles, and more ; and though they often descend to a much 
lower level, they present an inaccessible barrier on the northeast, 
while on the southwest they sink in gentle declivity to the 
plains. 

428. There is one remarkable feature in the Moon's surface 
which bears no analogy to anything observable on the Earth. 
This is the circular cavities which appear in every part of her 
disc. Some of these immense caverns are nearly four miles deep, 
and forty miles in diameter. They are the most numerous in the 
southwestern part. As they reflect the Sun's rays more 
copiously, they render this part of her surface more brilliant 
than any other. They present to us nearly the same appearance 
as our Earth might be supposed to present to the Moon if all 
our great lakes and seas were dried up. 

429. The number of remarkable spots on the Moon, whose 
latitude and longitude have been accurately determined, exceeds 
200. The number of seas and lakes, as they were formerly con- 
sidered, whose length and breadth are known, is between 20 and 
30 ; while the number of peaks and mountains, whose perpen- 
dicular elevation varies from a fourth of a mile to five miles in 
height, and whose bases are from one to seventy miles in length, 
is not less than one hundred and fifty. 

Graphical views of these natural appearances, accompanied with minute and familiar 
descriptions, constitute what is called Selenography, from two Greek words, which mean 
the same thing, in regard to the Moon, as Geography does in regard to the Earth. 

430. An idea of some of these scenes may be formed by con- 
ceiving a plane of about 100 miles in circumference, encircled by 
a range of mountains, of various forms, three miles in perpen- 
dicular height, and having a mountain near the center, whose 
top reaches a mile and a half above the level of the plain. From 
the top of this central mountain, the whole plain, with all its 
scenery, would be distinctly visible, and the view would be 
bounded only by a lofty amphitheatre of mountains, rearing their 
summits tc the sky. 

431. The bright spots of the Moon are the mountainous 
regions ; while the dark spots are the plains, or more level parts 
of her surface. There may be rivers or small lakes on this 

428. What remarkable feature of the Moon's surface noticed ? 429. What number 
of remarkable ^pots ] Of " seas or lakes ? " Of mountains ? What is Selenography f 
430. How conceive justly of the lunar scenery? 431. What are the brightest spots on 



214 ASTRONOMY. 

planet ; but it is generally thought, by astronomers of the present 
day, that there are no seas or large collections of water, as was 
formerly supposed. Some of these mountains and deep valleys 
are visible to the naked eye ; and many more are visible through 
a telescope of but moderate powers. 

432. A telescope which magnifies only 100 times will show a 
spot on the Moon's surface, whose diameter is 1223 yards ; and 
one which magnifies a thousand times, will enable us to perceive 
any enlightened object on her surface whose dimensions are only 
122 yards, which does not much exceed the dimensions of some 
of our public edifices, as for instance, the Capitol at Washington, 
or St. Paul's Cathedral. Some years since, Professor Frauen- 
hofer, of Munich, announced that he had discovered a lunar 
edifice, resembling a fortification, together with several lines of 
road. The celebrated astronomer Schroeter, conjectures the 
existence of a great city on the east side of the Moon, a little 
north of her equator, an extensive canal in another place, and 
fields of vegetation in another. 



CHAPTER Y. 

SOLAR AND LUNAR ECLIPSES. 

433. Of all the phenomena of the heavens, there are none 
which engage the attention of mankind more than eclipses of the 
Sun and Moon ; and to those who are unacquainted with astro- 
nomy, nothing appears more wonderful than the accuracy with 
which they can be predicted. In the early ages of antiquity, 
they were regarded as alarming deviations from the established 
laws of nature, presaging great public calamities, and other 
tokens of the divine displeasure. 

In China, the prediction and observance of eclipses are made a matter of state policy, 
in order to operate upon the fears of the ignorant, and impose on them a superstitious 
regard for the occult wisdom of their rulers. In Mexico, the natives fast and afflict them- 
selves, during eclipses, under an apprehension that the Great Spirit is in deep sufferance. 
Some of the northern tribes of Indians have imagined that the Moon had been wounded 
in a quarrel ; and others, that she was about to be swallowed by a huge fish. 

the Moon's surface? The dark ones? 432. How small objects maybe seen on the 
Moon's surface? What announcement by Erauenhofer? Conjecture of Sebvoeter? 
433. Subject of Chapter V.? Remark respecting eclipses? How regarded by the 
ancients? In China? Mexico? By northern Indians? Anecdote of Columbus ? 



SOLAR AND LUNAR ECLIPSES. 215 

It was by availing himself of these superstitious notions, that Columbus, when ship- 
wrecked on the island of Jamaica, extricated himself and crew from a most embarrass- 
ing condition. Being driven to great distress for want of provisions, and the natives 
refusing him any assistance, when all hope seemed to be cut off, he bethought himself of 
their superstition in regard to eclipses. Having assembled the principal men of the 
island, he remonstrated against their inhumanity, as being offensive to the Great Spirit: 
and told them that a great plague was even then ready to fall upon them, and as a token 
of it, they would that night see the Moon hide her face in anger, and put on a dreadfully 
dark and threatening aspect. This artifice had the desired effect; for the eclipse had no 
sooner begun, than the frightened barbarians came running with all kinds of provisions, 
and throwing themselves at the feet of Columbus, implored his forgiveness. — Almagest, 
vol. I., 55 c. v. 2. 

434. An eclipse of the Sun takes place, when the dark body 
of the Moon, passing directly between the Earth and the Sun, 
intercepts his light. This can happen only at the instant of new 
moon, or when the Moon is in conjunction ; for it is only then 
that she passes between us and the Sun. 

An eclipse of the Moon takes place when the dark body of 
the Earth, coming between her and the Sun, intercepts his light, 
and throws a shadow on the Moon. This can happen only at the 
time of full moon, or when the Moon is in opposition ; for it is 
only then that the Earth is between her and the Sun. 

435. As every planet belonging to the solar system, both pri- 
mary and secondary, derives its light from the Sun, it must cast 
a shadow towards that part of the heavens which is opposite to 
the Sun. If the Sun and planet were both of the same magni- 
tude, the form of the shadow cast by the planet, would be that 
of a cylinder, and of the same diameter as the Sun or planet. 

CYLINDRICAL SHADOW. 





Here the Sun and planet are represented as of the same size, and the shadow of the 
latter is in the form of a cylinder. 

436. If the planet were larger than the Sun, the shadow would 
continually diverge, and grow larger and larger ; but as the Sun 
is much larger than any of the planets, the shadows which they 
cast must converge to a point in the form of a cone, the length 
of which will be proportional to the size and distance of the 
planet from the Sun. 



434. When do solar eclipses occur? Why only then? Lunar? Why only at full 
moon? 435. Do all the planets cast shadows? Suppose the Sun and planet were of 
the same size, what would be the form of their shadows? 436. What if the planet was 
largest? How as they are smaller than the Sun? How is the length of the shadow 
modified by the distance of the planet from the Sun ? 



216 



ASTRONOMY. 



DIVERGING SHADOW. 




A _ 



In this cut, the opaque body is the larger, and the shadow projected from it dvoerges, 
or grows more broad as the distance from the planet increases. 

If the opaque body is smaller than the luminous one, the shadow converges to a 
point. 

CONVERGING SHADOW. 




Here the luminous tody is the larger, and the shadow converges to a p</int, and takes 
the form of a cone. 

The opaque body being smaller than the luminous one, the length of its shadow will be 
modified by its distance, as in the following : 



Here, also, the luminous body is the larger, and both precisely of the s;„me size as in 
the cut preceding; but being placed nearer each other, the shadow is shown to be con- 
siderably shorter. 

43t. All the planets, both primaries and secondaries, cast 
shadows in a direction opposite the Sun (see cut on rext page). 
The form and length of these shadows depend upon the compara- 
tive magnitude of the Sun and planet, and their distance from 
each other. If the Sun and a planet were of the same size, the 
shadow of the planet would be in the form of a cylinder, what- 
ever its distance. If the planet was larger than the Sun, the 
shadow would diverge, as we proceed from the planet off into 
space ; and the nearer the Sun, the more divergent the shadow 
would be. But as the planets are all much smaller than the 
Sun, the shadows all converge to a point, and take the form of a 
cone; and the nearer to the Sun, the shorter their shadows. 



437. Why have the largest and most distant planets the longest shadows ? Do any of 
the primary planets eclipse each other? 



SOLAR AND LUNAR ECLIPSES. 217 

SHADOWS OF THE PLANETS. 



These principles are partly illus- 
trated in the adjoining cut. The 
planets nearest the Sun have com- 
paratively short shadows, while those 
more remote extend to a great dis- 
tance. No primary, however, casts a 
shadow long enough to reach the next 
exterior planet. 

The magnitude of the Sun is such, 
that the shadow cast by each of the 
primary planets always converges to 
a point before it reaches any other 
planet; so that not one of the pri- 
mary planets can eclipse another. 
The shadow of any planet which is 
accompanied by Satellites, may, on 
certain occasions, eclipse its satel- 
lites ; but it is not long enough to 
eclipse any other body. The shadow 
of a satellite or Moon, may also, on 
certain occasions, fall on the primary, 
and eclipse it. 











S^ 




/ 


i 






•-. \ \ 


\ 








r# * : ) | 




\ 

\ 


\ 


# 


S3- : 




1 


\ 


\, 


""-->.. 




- y y 


f 



438. When the Sun is at his greatest distance from the Earth, 
and the Moon at her hast distance, her shadow is sufficiently 
long to reach the Earth, and extend 19,000 miles beyond. 
When the Sun is at his least distance from the Earth, and the 
Moon at her greatest, her shadow will not reach the Earth's sur- 
face by 20,000 miles. So that when the Sun and Moon are at 
their mean distances, the cone of the Moon's shadow will termi- 
nate a little before it reaches the Earth's surface. 

In the former case, if a conjunction take place when the center of the Moon comes in a 
direct line between the centers of the Sun and Earth, the dark shadow of the Moon will 
fall centrally upon the Earth, and cover a circular area of 175 miles in diameter. To all 
places lying within this dark spot, the Sun will be totally eclipsed, as illustrated by the 
figure. 

439. Eclipses of the Sun must always happen at New Moon, 
and those of the Moon at Full Moon. The reason of this is, 
that the Moon can never be between us and the Sun, to eclipse 
him, except at the time of her change, or New Moon ; and she 
can never get into the Earth's shadow, to be eclipsed herself, 
except when she is in opposition to the Sun, and it is Full 
Moon. 

440. If the Moon's orbit lay exactly in the plane of the eclip- 
tic, she would eclipse the Sun at every change, and be eclipsed 
herself at every full ; but as her orbit departs from the ecliptic 
over 5° (422), she may pass either above or below the Sun at 

438. What is the length of the Moon's shadow when she is nearest the Earth and 
farthest from the Sun? What when nearest the Sun and farthest from the Earth? 
What when the Sun and Moon are at their mean distances ? 489. At what time of the 
Moon do solar eclipses always occur? Lunar? Why? 440. Why not two solar and 



218 ASTRONOMY. 

the time of her change, or above or below the Earth's shadow 
at the time of her full. 

NEW AND FULL MOONS WITHOUT ECLIPSES. 
Shadow above the Earth. Above the Earth's shadow. 






Shadow below the Earth. Below the Earth"s shadow. 



Let theline joining the Earth and the Sun represent the plane of the ecliptic. Now as 
the orbit of the Moon departs from this plane about 5° 9', she may appear either above 
or below the Sun at New Moon, as represented in the figure, and her shadow may fall 
above the north pole or below the south. At such times, then, there can be no solar 
eclipse. 

On the right, the Moon is shown at her full, both above and below the Earth's shadow, 
in which case there can be no lunar eclipse. 

441. As the Moon passes from one of her nodes to the other 
in 1*73 days, there is just this period between two successive 
eclipses of the Sun, or of the Moon. In whatever time of the 
year, then, we have eclipses at either node, we may be sure that 
in 173 days afterwards, we shall have eclipses at the other node. 

As the Moon's nodes fall back, or retrograde in the ecliptic, at the rate of 19^° every 
year, they will complete a backward revolution entirely around the ecliptic to the same 
point again, in 18 years, 225 days ; in which time there would always be a regular period 
of eclipses, if any complete number of lunations were finished without a remainder. But 
this never happens; for if both the Sun and Moon should start from a line of conjunction 
with either of the nodes in any point of tha ecliptic, the Sun would perform 18 annual 
revolutions and 222° of another, while the Moon would perform 230 lunations, and 85° of 
another, before the node would come around to the same point of the ecliptic again ; so 
that the Sun would then be 138* from the node, and the Moon 85° from the Sun. 

But after 223 lunations, or 18 years, 11 days, 7 hours, 42 minutes, and 31 seconds, the 
Sun, Moon, and Earth, will return so nearly in the same position with respect to each 
other, that there will be a regular return of the same eclipses for many ages. This 
grand period was discovered by the Chaldeans, and by them called Saros. If, therefore, 
to the mean time of any eclipse, either of the Sun or Moon, we add the Chaldean period 
of IS years and 11 days, we shall have the return of the same eclipse. This mode of pre- 
dicting eclipses will hold good for a thousand years. In this period there are usually 70 
eclipses ; 41 of the Sun and 29 of the Moon. 

442. The diameter of the Earth's shadow, at the distance of 
the Moon, is nearly three times as large as the diameter of the 
Moon ; and the length of the Earth's shadow is nearly four times 
as great as the distance of the Moon ; exceeding it in the same 
ratio that the diameter of the Earth does the diameter of the 
Moon, which is as 3.663 to 1. 

443. The number of eclipses in any one year, cannot be less 
than two, nor more than seven. In the former case, they will 

two lunar eclipses every lunar month? 441. How often may eclipses occur at oppo- 
site nodes? What cycle of eclipses described? Number of eclipses in this cycle? 
442. What is the diameter of the Earth's shadow at the distance of the Moon ? 443. 
What number of eclipses may occur in any one year? If but two, what will they be? 



SOLAR AND LUNAR ECLIPSES. 



219 



both be of the Sun ; and in the latter, there will be five of the 
Sun, and two of the Moon — those of the Moon will be total. 
There are sometimes six ; but the usual number is four : two of 
the Sun, and two of the Moon. 

The cause of this variety is thus accounted for. Although the Sun usually passes 
by both nodes only once in a year, he may pass the same node again a little before 
the end of the year. In consequence of the retrograde motion of the Moon's nodes, 
he will ,come to either of them 173 days after passing the other. He may, there- 
fore, return to the same node in about 346 days, having thus passed one node twice, and 
the other once, making each time, at each, an eclipse of both the Sun and the Moon, or 
six in all. And since 12 lunations, or 354 days from the jftrst eclipse, in the beginning of 
the year, leave room for another New Moon before the close of the year, and since this 
New Moon may fall within the ecliptic limit, it is possible for the Sun to be eclipsed again. 
Thus there may be seven eclipses in the same year. 



LUNAK ECLIPSE. 



SOLAR ECLIPSE. 




444. Eclipses of the Sun always come on from the west, and 
pass over eastward ; while eclipses of the Moon come on from 

the east, and pass over westward. 
This is a necessary result of the 
eastward motion of the Moon in 
her orbit. 

In the right hand cut, the Moon is seen 
revolving eastward, throwing her shadow upon 
the Earth, and hiding the western limb of the 
Sun. In some instances, however, when the 
eclipse is very slight, it may first appear on the 
northern or southern limb of the Sun — that is, 
the upper or lower side ; but even then its 
direction must be from west to east. It will 
also be obvious from this figure, that the sha- 
dow of the Moon upon the Earth must also tra- 
verse her surface from west to east; conse- 
quently the eclipse will be visible earlier in the 
west than in the east. 

Oh the left, the Moon is seen striking into 
the Earth's shadow from the west, and having 
her eastern limb first obscured. By holding the 
book up south of him, the student will see at 
once why the revolution of the Moon eastward 
must cause a solar eclipse to proceed from west 
to east, and a lunar eclipse from east to west. 
To locate objects and motions correctly, the 
student should generally imagine himself look- 
ing to the south, as we are situated north of the 
equinoctial. The student should bear in mind 
that nearly all the cuts in the bonk are drawn 
to represent a view from northern latitude 
upon the Earth. Hence, by holding the book 
up south of him, the cuts will generally afford 
an accurate illustration both of the positions 
and motions of the bodies represented. 

445. The time which elapses between two successive changes 
of the Moon is called a Lunation, which, at a mean rate, is about 






If seven ? What is the usual number ? Can you explain the cause of this variety ? 
444. What is the direction of a solar eclipse? A lunar? Why this difference? 445. 
What is a lunation ? What would be the effect if the solar and lunar months were 
equal ? What result from the existing inequality ? 



B.G. 



10 



220 ASTRONOMY. 

29^- days. If 12 lunar months were exactly equal to the 12 solar 
months, the Moon's nodes would always oceupy the same points 
in the ecliptic, and all eclipses would happen in the same months 
of the year, as is the case with the transits of Mercury and 
Venus : but, in 12 lunations, or lunar months, there are only 
354 days ; and in this time the Moon has passed through both 
her nodes, but has not quite accomplished her revolution around 
the Sun ; the consequence is, that the Moon's nodes fall back in 
the ecliptic at the rate of about 19-^° annually ; so that the 
eclipses happen sooner every year by about 19 days. 

446. Eclipses can never take place, except when the Moon 
is near the ecliptic ; or, in other words, at or near one of her 
nodes. At all other times, she passes above or below the Sun, 
and also above or below the Earth's shadow. It is not neces- 
sary that she should be exactly at her node, in order that an 
eclipse occur. If she is within 11° of her node, at the time of 
her change, she will eclipse the Sun ; and if within 12° of her 
node at her full, she will strike into the Earth's shadow, and be 
more or less eclipsed. These distances are called, respectively, 
the solar and lunar ecliptic limits. 

This subject may be understood by consulting the following figure : 

THE MOON CHANGING AT DIFFERENT DISTANCES FROM HER NODES. 





■ ^==:=s 









Let the line E E represent the ecliptic, and the line O the plane of the Moon's 
orbit. The light globes are the Sun, and the dark ones the Moon, which maybe imagined 
as much nearer the student ; hence their apparent diameter is the same. 

Let the point A. represent the node of the Moon's orbit. Now if the change occur 
when the Moon is at B, she will pass below the Sun. If when at C, she will just touch hia 
lower limb. At C, she will eclipse him a little, and so on to A ; at which point, if the 
change occurs, the eclipse would be central, and probably total. 

If the Moon was at G-, H, I, or J, in her orbit, when the change occurred, she would 
eclipse the upper or northern limb of the Sun, according to her distance from her node 
at the time ; but if she was at K, she would pass above the Sun, and would not eclipse 
him at all. The points C and J will represent the Solar Ecliptic Limits. 

The mean ecliptic limit for the Sun is 16j£° on each side of the node ; the mean eclip- 
tic limit for the Moon is 10%° on each side of the node. In the former case, then, there 
are 33 degrees about each node, making, in all, 66° out of 360°, in which eclipses of the 
Sun may happen ; in the latter case there are 21° about each node, making, in all, 42° 
o»t of 360° in which eclipses of the Moon usually occur. The proportion of the solar to 
fhe lunar eclipses, therefore, is as 66 to 42, or as 11 to 7. Yet, there are more visible 
••clipses of the Moon, at any given place, than of the Sun ; because a lunar eclipse is 
visible to a whole hemisphere, a solar eclipse only to a small portion of it. 

447. All parts of a planet's shadow are not alike dense. The 

446. Where must the Moon be, with respect to the ecliptic and her nodes, in order to 
an eclipse ? What meant by ecliptic limits t Name the distance of each, respectively, 
from the node. Illustrate. 447. What is the umbra of the Earth or Moon ? The 



SOLAR AND LUNAR ECLIPSES. 221 

darkest portion is called the umbra, and the partial shadow the 
penumbra. 

UMBRA AND PENUMBRA OF THE EARTH AND MOON. 




Penumbra is from the Latin pene, almost, and umbra, a shadow. In this cut, the 
Earth's umbra and penumbra will be readily found by the lettering ; while A is the umbra, 
and B B the penumbra, of the Moon. The latter is more broad than it should be, owing 
to the nearness of the Sun in the cut, as it never extends to much over half the Earth's 
diameter. The student will see at once that solar eclipses can be total only to persons 
within the umbra ; while to all on which the penumbra falls, a portion of the Sun's disc 
will be obscured. 

448. The average length of the Earth's umbra is about 
860,000 miles ; and its breadth, at the distance of the Moon, is 
about 6000 miles, or three times the Moon's diameter. 

As both the Earth and Moon revolve in elliptical orbits, both the above estimates are 
subject to variations. The length of the Earth's umbra varies from 842,217 to 871,262 
miles ; and its diameter, where the moon passes it, varies from 5235 to 6365 miles. 

449. The average length of the Moon's umbra is about 
239,000 miles. It varies from 221,148 to 252,638 miles, 
according to the Moon's distance from the Sun. Its greatest 
diameter, at the distance of the Earth, is 110 miles ; but the 
penumbra may cover a space on the Earth's surface 4393 miles 
in diameter. 

When the Moon but just touches the limb of the Sun, or the 
umbra of the Earth, it is called an appulse (see C and J in the 
cut on the opposite page). 

450. A partial eclipse is one in which only part of the Sun or 
Moon is obscured. A solar eclipse is partial to all places 
outside the umbra ; but within the umbra, where the whole 
disc is obscured, the eclipse is said to be total. A central eclipse 
is one taking place when the Moon is exactly at one of her nodes. 
If lunar, it is total, as the Earth's umbra is always broad enough, 
at the Moon's distance, if centrally passed, to obscure her whole 
disc. But a solar eclipse may be central and not. total, as the 
Moon is not always of sufficient apparent diameter to cover the 

penumbra t Derivation ? Within which are solar eclipses total ? 448. The average 
length of the Earth's shadow ? Breadth at the Moon's distance ? Do they vary ? Why? 
449. Average length of the Moon's umbra ? Does it vary ? Why ? Greatest diameter 
at the Earth's surface? Of penumbra? What is an appulse? 450. A partial 
eclipse ? A total ? A central ? Are all central eclipses total ? Why not ? What called 
then? Why? 



222 



ASTRONOMY. 



whole disc of the Sun. In that case, the eclipse would be 
annular (from annulus, a ring), because the Moon only hides the 
center of the Sun, and leaves a bright ring unobscured. 



Going oS. 


PROGRESS OF A CENTRAL ECLIPSE. 
Annular. 


Coming on. 


— — ■■—— ■•■ ■ — - - — ■ -~ - — -;-■ " — -~ ^ ' =| 


D 


■ 


^=""1^^! 


S3 


xSS^Smt 


imi 


a«€^^ 



451. It has already been shown that the apparent magni- 
tudes of bodies vary as their distances vary ; and as both the 
Earth and Moon revolve in elliptical orbits, it follows that the 
Moon and Sun must both vary in their respective apparent mag- 
nitudes. Hence some central eclipses of the Sun are total, 
while others are partial and annular. 



TOTAL AND ANNULAR ECLIPSES OF THE SUN. 




At A, the Earth is at her aphelion, and the Sun being at his most distant point, will 
have his least apparent magnitude. At the same time, the Moon is in perigee, and 
appears larger than usual. If, therefore, she pass centrally over the Sun's disc, the 
eclipse will be total. 

At B, this order is reversed. The Earth is at her perihelion, and the Moon in apogee; 
bo that the Sun appears larger, and the Moon smaller than usual. If, then, a central 
eclipse occur under these circumstances, the Moon will not be large enough to eclipse the 
whole of the Sun, but will leave a ring, apparently around herself, unobscured. Such 
eclipse will be annular. 

452. The greatest possible duration of the annular appearance 
of a solar eclipse, is 12 minutes and 24 seconds; and the greatest 
possible time during which the Sun can be totally eclipsed, to 
any part of the world, is T minutes and 58 seconds. The Moon 
may continue totally eclipsed for one hour and three quarters. 

553. As the solar ecliptic's limits are further from the Moon's 
nodes than the lunar, it results that we have more eclipses of 
the Sun than of the Moon. There may be seven in all in one 

451. Why are some central eclipses total, and others partial and annular? 452. 
How long may an annular eclipse continue ? A total eclipse of the Sun ? Of the Moon? 
453. Which kind of eclipses is most frequent? Why? The greatest number in a year ? 



SOLAR AND LUNAR ECLIPSES. 223 

year, viz., five solar and two lunar ; but the most usual number 
is four. There can never be less than two in a year ; in which 
case, both must be of the Sun. Eclipses both of the Sun and 
Moon recur in nearly the same order, and at the same intervals, 
at the expiration of a cycle of 223 lunations, or 18 years of 365 
days and 15 hours. This cycle is called the Period of the 
Eclipses. At the expiration of this time, the Sun and the 
Moon's nodes will sustain the same relation to each other as at 
the beginning, and a new cycle of eclipses begins. 

454. In a total eclipse of the Sun, the heavens are shrouded 
in darkness, the planets and stars become visible, the tempera- 
ture declines, the animal tribes become agitated, and a general 
gloom overspreads the landscape. Such were the effects of the 
great eclipse of 1806. In a lunar eclipse, the Moon begins to 
lose a portion of her light and grows dim, as she enters the 
Earth's penumbra, till at length she comes in contact with the 
umbra, and the real eclipse begins. 

455. In order to measure and record the extent of eclipses, 
the apparent diameters of the Sun and Moon are divided into 
twelve equal parts, called digits; and in predicting eclipses, 
astronomers usually state which "limb" of the body is to be 
eclipsed — the southern or northern — the time of the first con- 
tact, of the nearest approach of centers, direction, and number 
of digits eclipsed. 

FIVE DIGITS ECLIPSED. TWELVE DIGITS. 



€^Z5>fe <* 1 * r,r *ifr' 





456. The last annular eclipse visible in the United States, 
occurred May 26, 1854. The next total eclipse of the Sun will 
be August 1, 1869. 

Some of the ancients, and all barbarous nations, formerly 
regarded eclipses with amazement and fear, as supernatural 
events, indicating the displeasure of the gods. Columbus is said 

How many of each? Least number, and which? Usual number? What said of the 
order of eclipses ? Time of cycle ? 454. Describe the effects of a total eclipse of the 
Fan. The process of a lunar eclipse? 455. How are eclipses measured and recorded? 
456. When the next annular eclipse visible in this country ? The next total ? How have 



224 



ASTRONOMY. 



to have made a very happy use of this superstition, as already 
stated on a previous page. (Art. 433.) 

457. Eclipses can be calculated with the greatest precision, 
not only for a few years to "come, but for centuries and ages 
either past or to come. This fact demonstrates the truth of the 
Copernican theory, and illustrates the order and stability that 
everywhere reign throughout the planetary regions. 

The following is a list of all the solar eclipses that will be visible in Europe and America 
during the remainder of the present century. To those which will be visible in New 
England, the number of digits is annexed. 



Year. 


Month. 


Day and hour. 


Digits. 


Year. 


Month. 


Day and hour. 


Digits. 


1858, 


Mar. 


15 6 14 A. 


M. 


1% 


1878, 


July 


29 4 56 P. M. 


TH 


1859, 


July 


29 5 32 P. 


M. 


2% 


1879, 


July 


19 2 A. M. 




1860, 


July 


18 7 23 A. 


M. 


6% 


1S80, 


Dec. 


31 7 30 A. M. 


5% 


1861, 


Dec. 


31 7 30 A. 


M. 


±% 


1882, 


May 


17 1 A. M. 




1863, 


May 


17 1 P. 


M. 




1885, 


Mar. 


16 35 A. M. 


6% 


1865, 


Oct. 


19 9 10 A. 


M. 


8% 


1886, 


Aug. 


29 6 30 A. M. 


0% 


1866, 


Oct. 


8 11 12 A. 


M. 





1887, 


Aug. 


18 10 P. M. 




1867, 


Mar. 


6 8 A. 


M. 




1890, 


June 


17 3 A. M. 




1868, 


Feb. 


23 10 A. 


M. 




1891, 


June 


6 Mer. 




1869, 


Aug. 


7 5 21 A. 


M. 


10% 


1S92, 


Oct. 


20 19 P. M. 


8% 


1870, 


Dec. 


22 6 A. 


M. 




1S95, 


Mar. 


26 4 A. M. 




1873, 


May 


26 3 A. 


M. 




1896, 


Aug. 


9 Mer. 




1874, 


Oct. 


10 4 A. 


M. 




1897, 


July 


29 9 8 A. M. 


4% 


1875, 


Sept, 


29 5 56 A. 


M. 


11% 


1899, 


June 


8 Mer. 




1876, 


Mar. 


25 4 11 P. 


M. 


3% 


1900, 


May 


28 8 9 A. M. 


11 



The eclipses of 1869, 1875, and 1900 will be very large. In those of 1858, 1861, 1873, 
1875, and 18S0, the Sim will rise eclipsed. 

That of 1S75 will be annular'. The scholar can continue this table, or extend it back- 
wards, by adding or substracting the Chaldean period of 18 years, 11 days, 7 hours, 54 
minutes, and 31 seconds. 



CHAPTER VI. 



PRIMARY PLANETS CONTINUED— MARS AND THE 
ASTEROIDS. 

458. Mars is the first of the exterior planets, its orbit lying 
immediately without, or beyond, that of the Earth, while those 
of Mercury and Venus are within. He appears, to the naked 
eye, of a fine ruddy complexion ; resembling, in color, and appa- 

the ignorant and superstitious regarded eclipses? 457. What said of the calculation of 
eclipses? What does this demonstrate and illustrate? 458. Position of Mars' orbit? 
How does he appear to the naked eye? When most brilliant? When least? 



THE PRIMARY PLANETS MARS AND THE ASTEROIDS. 225 

rent magnitude, the star Antares, or Aldebaran, near which it 
frequently passes. It exhibits its greatest brilliancy about the 
time that it rises when the Sun sets, and sets when the Sun 
rises • because it is then nearest the Earth. It is least brilliant 
when it rises and sets with the Sun; for then it is five times farther 
removed from us than in the former case. 

459. Its distance from the Earth at its nearest approach is 
about 50,000,000 of miles. Its greatest distance from us is 
about 240,000,000 of miles. In the former case, it appears 
nearly 25 times larger than in the latter. When it rises before 
the Sun, it is our morning star ; when it sets after the Sun, it is 
our evening star. 

The distance of all the planets from the Earth, whether they be interior or exterior 
planets, varies within the limits of the diameters of their orbits ; for when a planet is 
in that point of its orbit which is nearest the Earth, it is evidently nearer by the whole 
diameter of its orbit, than when it is in the opposite point, on the other side of its orbit. 
The apparent diameter of the planet will also vary for the same reason, and to the 
same degree. 

460. Mars is sometimes seen in opposition to the Sun, and 
sometimes in superior conjunction with him ; sometimes gibbous, 
but never horned. In conjunction, it is never seen to pass over 
the Sun's disc, like Mercury and Venus. These prove not only 
that its orbit is exterior to the Earth's orbit, but that it is an 
opaque body, shining only by the reflection of the Sun. 

461. The motion of Mars through the constellations of the 
zodiac is but little more than half as great as that of the Earth; 
it being generally about 57 days in passing over one sign, which 
is at the rate of a little more than half a degree each day. Thus, 
if we know what constellation Mars enters to-day, we may con- 
clude that two months hence it will be in the next constellation ; 
four months hence, in the next ; six months, in the next, and 
so on. 

Its mean sidereal revolution is performed in 6S6.979645S solar days ; or in 686 days, 23 
hours, 30 minutes, 41.4 seconds. Its synodical revolution is performed in 779.936 solar 
days ; or in 779 days, 22 hours, 27 minutes, and 50 seconds. 

462. Mars performs his revolution around the Sun in one 
year and 10|- months, at the distance of 145,000,000 of miles ; 
moving in its orbit at the mean rate of 55,000 miles an hour. 
Its diurnal rotation on its axis is performed in 24 hours, 39 

459. Its distance from the Earth? What effect upon its apparent magnitude? When 
morning and evening star ? How do the distances of the planets from the Earth vary ? 
Their apparent diameters? 460. Is Mars ever in opposition to the Sun? In conjunc- 
tion t Its phases? Does it ever transit the Sun? What do these facts prove ? 461. 
What is his rate of motion through the constellations ? What calculation based upon it ? 
462. His periodic time ? Distance from the Sun? Mean rate of motion per hour? Time 
of rotation on his axis? How does his day compare with ours? 



226 ASTRONOMY. 

minutes, and 21-J- seconds ; which makes its day about 44 min- 
utes longer than ours. 

463. Its form is that of an oblate spheroid, whose polar 
diameter is to its equatorial, as 15 is to 16, nearly. Its diameter 
is 4,222 miles. Its bulk, therefore, is 7 times less than that of 
the Earth ; and being 50,000,000 of miles farther from the Sun, 
it receives from him only half as much light and heat. 

464. The inclination of its axis to the plane of its orbit, is 
about 28f °. Consequently, its seasons must be very similar to 
those of the Earth. Indeed, the analogy between Mars and the 
Earth is greater than the analogy between the Earth and any 
other planet of the solar system. Their diurnal motion, and of 
course the length of their days and nights, are nearly the same ; 
the obliquity of their ecliptics, on which the seasons depend, are 
not very different ; and, of all the superior planets, the distance 
of Mars from the Sun is by far the nearest to that of the Earth ; 
nor is the length of its year greatly different from ours, when 
compared with the years of Jupiter, Saturn and Uranus. 

465. To a spectator on this planet, the Earth will appear 
alternately, as a morning and evening star ; and will exhibit all 
the phases of the Moon, just as Mercury and Yenus do to us ; 
and sometimes like them, will appear to pass over the Sun's disc 
like a dark round spot. Our Moon will never appear more than 
a quarter of a degree from the Earth, although her distance from 
it is 240,000 miles. If Mars be attended by a satellite, it is too 
small to be seen by the most powerful telescopes. 

When it is considered that Vesta, the smallest of the asteroids, which is once and a 
half 'times the distance of Mars from us, and only 269 miles in diameter, is perceivable 
in the cpen space, and that without the presence of a more conspicuous body to point it 
out, we may reasonably conclude that Mars is without a Moon. 

466. The progress of Mars in the heavens, and indeed of all 
the superior planets, will, like Mercury and Venus, sometimes 
appear direct, sometimes retrograde, and sometimes he will seem 
statiouary. The portion of the ecliptic through which a planet 
seems to retrograde is called the Arc of Retrogradation. The 
more remote the planet the less the arc, and the longer the time 
of its retrogression. These retrograde movements and stations, 
as they appear to a spectator from the Earth, are common to 
all the planets, and demonstrate the truth of the Copernican 
system. 

463. Form of Mars? Diameter? Bulk? Light and heat? 464. Inclination of his 
axis to the plane of his orbit? His seasons? Resemblance to our globe? 465. How 
would the Earth appear to a spectator upon Mars ? Our Moon ? Has Mars a satellite ? 
466. What said of the motions of Mars and the other planets? What constitutes the 



THE PRIMARY PLANETS MARS AND THE ASTEROIDS. 227 

RETROGRADE MOTION OF THE EXTERIOR PLANETS. 
■M A 

a -f -'■■--.. 

4 <=d f m I 

i : "--o--*' 

D 

Suppose the Earth at A, and the planet Neptune at B, he would then appear to be at C, 
among the stars ; but as Neptune moves but a little from B toward F, while the Earth is 
passing from A to D, Neptune will appear to retrograde from C to E. Whatever Neptune 
may have moved, however, from B toward E, will go to reduce the amount of apparent 
retrogression. 

It is obvious from this figure, that the more distant an exterior planet is, and the slower 
it moves, the less will be its arc of retrogradation, and the longer will it be retrograding. 
Neptune appears to retrograde 180 days, or nearly half the year. 

The following table exhibits the amount of arc and the time of the retrogradation of 
the principal planets : 

Are. Days. 

Mercury 13^° 23 

Venus 16 42 

Mars 16 73 

Jupiter 10 121 

Saturn 6 139 

Uranus 4 151 

Neptune 1 180 

TELESCOPIC APPEARANCES OP MARS. 




The right-hand figure represents Mars as seen at the Cincinnati Observatory, August 5, 
1845. On the 30th of the same month he appeared as represented on the left. The 
middle mew is from a drawing by Dr. Dick. 

46 1. The telescopic phenomena of Mars afford peculiar interest 
to astronomers. They behold its disc diversified with numerous 
irregular and variable spots, and ornamented with zones and 
belts of varying brilliancy, that form, and disappear, by turns. 
Zones of intense brightness are to be seen in its polar regions, 
subject, however, to gradual changes. That of the southern 
pole is much the most brilliant. Dr. Herschel supposes that 
they are produced by the reflection of the Sun's light from the 
frozen regions, and that the melting of these masses of polar ice 
is the cause of the variation in their magnitude and appearance. 



Arc of Retrogradation ? What do these motions prove? 467. How does Mars appear 
through a telescope ? Dr. Herschel's opinion of Its polar regions ? How confirmed in 

10* 



228 ASTRONOMY. 

He was the more confirmed in these opinions by observing that after the exposure of 
the luminous zone about the north pole to a summer of eight months, it was considerably 
decreased, while that on the south pole, which had been in total darkness during eight 
months, had considerably increased. He observed, farther, that when this spot was 
most luminous, the disc of Mars did not appear exactly round, and that the bright part 
of its southern limb seemed to be swollen or arched out beyond the proper curve. 

468. The extraordinary height and density of the atmosphere 
of Mars, are supposed to be the cause of the remarkable redness 
of its light. It has been found, by experiment, that when a 
beam of white light passes through any colorless transparent 
medium, its color inclines to red, in proportion to the density of 
the medium, and the space through which it has traveled. Thus 
the Sun, Moon, and stars, appear of a reddish color when near 
the horizon ; and every luminous object, seen through a mist, is 
of a ruddy hue. 

This phenomena may be thus explained : — The momentum of the red, or least refrangi- 
ble rays, being greater than that of the violet, or most refrangible rays, the former will 
make their way through the resisting medium, while the latter are either reflected or 
absorbed. The color of the beam, therefore, when it reaches the eye, must partake of 
the color of the least refrangible rays, and this color must increase with the distance. 
The dim light, therefore, by which Mars is illuminated, having to pass twice through its 
atmosphere before it reaches the Earth, must be deprived of a great proportion of its 
violet rays, and consequently then be red. Dr. Brewster supposes that the difference of 
color among the other planets, and even the fixed stars, is owing to the different heights 
and densities of their atmospheres. 



THE ASTEROIDS, OR TELESCOPIC PLANETS. 

469. Ascending higher in the solar system, we find, between 
the orbits of Mars and Jupiter, a cluster of twenty-seven small 
planets, which present a variety of anomalies that distinguish 
them from all the older planets of the system. -Their names are 
Flora, Clio, Yesta, Iris, Metis, Eunomia, Psyche, Thetis, Melpo- 
mene, Fortuna, Massilia, Lutetia, Calliope, Thalia, Hebe, Parthe- 
nope, Irene, Egeria, Astrsea, Juno, Ceres, Pallas, and Hygeia. 
These, and four others whose names have not yet been announced, 
have all been discovered during the present century. 

470. The scientific Bode entertained the opinion, that the 
planetary distances, above Mercury, formed a geometrical series, 
each exterior orbit being double the distance of its next interior 
one, from the Sun ; a fact which obtains with remarkable exact- 
ness between Jupiter, Saturn, and Uranus. But this law seemed 
to be interrupted between Mars and Jupiter. Hence he inferred, 
that there was a planet wanting in that interval ; which is now 

this opinion ? 468. Supposed cause of the ruddy color of Mars ? Philosophical expla- 
nation ? Dr. Brewster's opinion ? 469. Position and number of the asteroids ? When 
discovered? 470. Bode's theory? What seeming interruption? What conclusion? 



Mercury 


4 


= 


4 


Asteroids 


Venus 


4 + 3x1 


= 


7 


Jupiter 


The Earth 


4+3x2 


= 


10 


Saturn 


Mars 


4+3x22 


= 


16 


Herschel 



THE PRIMARY PLANETS MARS AND THE ASTEROIDS. 229 

happily supplied by the discovery of the numerous star-form 
planets, occupying the very space where the unexplained vacancy 
presented a strong objection to his theory. 

According to Bode, the distances of the planets may be expressed nearly as follows : the 
Earth's distance from the Sun being 10. 

4+3x23 = 28 
4 + 3x2^ = 52 
4+3 x2 D = 100 
4+3x26 = 196 

Comparing these values with the actual mean distances of the planets from the Sun, 
we cannot but remark the near agreement, and can scarcely hesitate to pronounce that 
the respective distances of the planets from the Sun, were assigned according to a law, 
although we are entirely ignorant of the exact law, and of the reason for that law. — 
Brinkley's Elements, p. 89. 

471. The Asteroids are much smaller in size than the older 
planets — they all revolve at nearly the same distances from the 
Sun, and perform their revolutions in nearly the same periods — 
their orbits are much more eccentric, and have a much greater incli- 
nation to the ecliptic — and what is altogether singular, except in 
the case of comets — some of their orbits cross each other ; so that 
there is even a possibility that two of these bodies may, some 
time, in the course of their revolutions, come into collision. 

The orbit of Yesta is so eccentric, that she is sometimes 
farther from the Sun than either Ceres, Pallas, or Juno, although 
her mean distance is many millions of miles less than theirs. The 
orbit of Yesta crosses the orbits of several other asteroids, in 
two opposite points. 

The student should here refer to the Figures, Map I. of the Atlas, and verify such of 
these particulars as are there represented. It would be well for the teacher to require 
him to observe particularly the positions of their orbits, and to state their different 
degrees of inclination to the plane of the ecliptic. 

472. From these and other circumstances, many eminent 
astronomers are of opinion, that these twenty-seven planets are 
the fragments of a large celestial body which once revolved 
between Mars and Jupiter, and which burst asunder by some 
tremendous convulsion, or some external violence. The dis- 
covery of Ceres, by Piazzi, on the first day of the present cen- 
tury, drew the attention of all the astronomers of the age to 
that region of the sky, and every inch of it was minutely explor- 
ed. The consequence was, that in the year following, Dr. Olbers, 
of Bremen, announced to the world the discovery of Pallas, 
situated not many degrees from Ceres, and very much resembling- 
it in size. 



How substantially justified? 471. Size of the asteroids? Distance from the Sun? 
Periodic time? forms of their orbits? Position with respect to the ecliptic? What 
other singularity in their orbits ? What remarkable facts respecting the orbit of Vesta ? 
472. What conclusion has been drawn from these facts ? Progress of discovery ? 



230 ASTRONOMY. 

4*73. From this discovery, Dr. Olbers first conceived the idea 
that these bodies might be the fragments of a former world ; and 
if so, that other portions of it might be found either in the same 
neighborhood, or else, having diverged from the same point, 
" they ought to have two common points of reunion, or two 
nodes in opposite regions of the heavens through which all the 
planetary fragments must sooner or later pass." 

414. One of these nodes he found to be in the constellation 
Yirgo, and the opposite one in the Whale ; and it is a remark- 
able coincidence that it was in the neighborhood of the latter 
constellation that Mr. Harding discovered the planet Juno. In 
order, therefore, to detect the remaining fragments, if any 
existed, Dr. Olbers examined, three times every year, all the 
small stars in Yirgo and the Whale ; and it was actually in the 
constellation Yirgo, that he discovered the planet Yesta. Since 
that time, twenty-three additional asteroids have been discovered, 
and it is not unlikely that still additional fragments of a similar 
description will hereafter be discovered. 

Dr. Brewster attributes the fall of meteoric stones to the 
smaller fragments of these bodies happening to come within the 
sphere of the Earth's attraction. 

Meteoric stones, or what are generally termed aerolites, are stones which sometimes 
fall from the upper regions of the atmosphere upon the Earth. The substance of which 
they are composed, is, for the most part, metallic ; but the ore of which it consists is not 
to be found in the same constituent proportions in any known substance upon the Earth. 
Their fall is generally preceded by a luminous appearance, a hissing noise, and a loud 
explosion ; and when fuund immediately after their descent, they are always hot, and 
usually covered with a black crust, indicating a state of exterior fusion. 

Their size varies iiom that of small fragments of inconsiderable weight to that of the 
most ponderous masses. They have been found to weigh from 300 pounds to several tons ; 
and they have descended to the earth with a force sufficient to bury them many feet 
under the surface. 

Some have supposed that they are projected from volcanoes in the Moon ; others that 
they proceed from volcanoes on the Earth; while others imagine that they are gene- 
rated in the regions of the atmosphere ; but the truth probably is not yet ascertained. In 
gome instances, these stones have penetrated through the roofs of houses, and proved 
destructive to the inhabitants. 

If we carefully compute the force of gravity in the Moon, we shall find that if a body 
were projected from her surface with a momentum that would cause it to move at the rate 
of 8200 feet in the first second of time, and in the direction of a line joining the centers 
of the Earth and Moon, it would not fall again to the surface of the Moon ; but would 
become a satellite to the Earth. Such an impulse might, indeed, cause it, even after 
many revolutions, to fall to the earth. The fall, therefore, of these stones, from the air, 
may be accounted for in this manner. 

Mr. Harte calculates, that even a velocity of 6000 feet in a second, would be sufficient 
to carry a body projected from the surface of the Moon beyond the power of her attrac- 
tion. If so, a projectile force three times greater than that of a cannon, would carry a 
a body from the Moon, beyond the point of equal attraction, and cause it to reach the 
Earth. A force equal to this is often exerted by our volcanoes, and by subterranean 
steam. Hence, there is no impossibility in the supposition of their coming from the Moon. 

473. Theory of Dr. Olbers ? 474. Where did he find these nodes? What remarkable 
coincidence? Dr. Olbers' efforts? Discoveries since? Dr. Brewster's idea respecting 
meteoric stones ? What are meteoric stones ? Circumstances of their fall ? Size and 
weight? Supposed origin? Could they have fallen from the Moon? What computations ? 



THE PRIMARY PLANETS MARS AND THE ASTEROIDS. 231 

475. Yesta appears like a star of the 5th or 6th magnitude, 
shining with a pare steady radiance, and is the only one of the 
asteroids which can be discerned by the naked eye. 

Juno revolves around the Sun in 4 years, 4-|- months, at the 
mean distance of 254,000,000 of miles, moving in her orbit at 
the rate of 41,000 miles an hour. Her diameter is estimated at 
1393 miles. This would make her magnitude 183 times less 
than the Earth's. The light and heat which she receives from 
the Sun is seven times less than that received by the Earth. 

The eccentricity of her orbit is so great, that her greatest 
distance from the Sun is nearly double her least distance ; so 
that, when she is in her perihelion, she is nearer the Sun by 
130,000,000 of miles, than when she is in her aphelion. This 
great eccentricity has a corresponding effect upon her rate of 
motion ; for being so much nearer, and therefore so much more 
powerfully attracted by the Sun at one time than at another, 
she moves through that half of her orbit which is nearest the 
Sun, in one-half of the time that she occupies in completing the 
other half. 

According to Schroeter, the diameter of Juno is 1425 miles ; and she is surrounded by 
an atmosphere more dense than that of any of the other planets. Schroeter also remarks 
that the variation in her brilliancy is chiefly owing to certain changes in the density of 
her atmosphere ; at the same time, he thinks it not improbable that these changes may 
arise from a diurnal revolution on her axis. 

476. Ceres revolves about the Sun in 4 years, T-J months, at 
the mean distance of 263,500,000 of miles, moving in her orbit 
at the rate of 41,000 miles an hour. Her diameter is estimated 
at 1582 miles, which makes her magnitude 125 times less than 
the Earth's. The intensity of the light and heat which she 
receives from the Sun is about 7-J times less than that of those 
received by the Earth. 

Ceres shines with a ruddy color, and appears to be only about 
the size of a star of the 8th magnitude. Consequently she is 
never seen by the naked eye. She is surrounded by a species 
of cloudy or nebulous light, which gives her somewhat the 
appearance of a comet, forming, according to Schroeter, an 
atmosphere 675 miles in height. 

Ceres, as has been said, was the first discovered of the asteroids. At her discovery, 
astronomers congratulated themselves upon the harmony of the system being restored. 
They had long wanted a planet to fill up the great void between Mars and Jupiter, in 
order to make the system complete in their own eyes ; but the successive discoveries of 

475. What is the appearance of Vesta ? Juno's period ? Distance from the Sun ? 
Rate of motion ? Diameter ? Relative magnitude ? Light and heat ? Eccentricity of 
orbit? Effect upon her orbitual motion? 476. Ceres' period and mean distance? 
Rate of motion ? Diameter? Relative magnitude ? Light and heat? Color and appa- 
rent size ? How seen? What said of her atmosphere ? Her discovery? 



232 



ASTRONOMY. 



Pallas and Juno again introduced confusion, and presented a difficulty which they were 
unable to solve, till Dr. Olbers suggested the idea that these small anomalous bodies were 
merely the fragments of a larger planet, which had been exploded by some mighty con- 
vulsion. Among the most able and decided advocates of this hypothesis, is Dr. Brewster, 
of Edinburgh. 

417. Pallas performs her revolution around the Sun in 4 
years, If months, at the mean distance of 264,000,000 of miles, 
moving in her orbit at the rate of 41,000 miles an hour. Her 
diameter is estimated at 2025 miles, which is but little less than 
that of our Moon. It is a singular and very remarkable phe- 
nomenon in the solar system, that two planets (Ceres and Pal- 
las), nearly of the same size, should be situated at equal dis- 
tances from the Sun, revolve about him in the same period, and 
in orbits that intersect each other. The difference in the respec- 
tive distances of Ceres and Pallas is less than a million of miles. 
The difference in their sidereal revolutions, according to some 
astronomers, is but a single day. 

The calculation of the latitude and longitude of the asteroids is a labor of extreme 
difficulty, requiring more than 400 equations to reduce their anomalous perturbations to 
the true place. This arises from the want of auxiliary tables, and from the fact that the 
elements of the star-form planets are very imperfectly determined. Whether any of the 
asteroids has a rotation on its axis, remains to be ascertained. 

The following Table contains most that is known of the asteroids to the present date 
(1855) : 

TABLE OF THE INTRRIOR PLANETS AND ASTEROIDS. 



Names. 


Mean distance 
from the Sun in 
miles. 


Period of revo- 
lution round tlie 
Sun in days. 


When 
discovered. 


By whom 
discovered. 


Where 
discovered. 


Mercury 

Venus 

The Earth 


209,160,265 
221,813,220 
224,302,695 
226,159,280 
226,632,665 
227,946,800 


1,193 
1,303 
1,325 
1,341 
1,345 
1,357 


Oct. 18, 1847 
Sept. 13, 1850 
March 29, 1807 
Aug. 13, 1847 
April 26, 1848 
July 29, 1851 
March 17, 1852 
April 17,1852 
June 24, 1852 
Aug. 22, 1852 
Sept. 21, 1852 
Nov. 15, 1852 
Nov. 16, 1852 


Hind 

Hind 

Olbers 

Hind 

Graham 

Gasparis . . . 
Gasparis . . . 

Luther 

Hind 

Hind 

Cliarconac... 
Goldschmit.. 
Hind 


London. 
London. 
Bremen. 
London. 




Markree. 


Clio 


Naples. 




Naples. 








Bilk, Ger 








London. 








London. 








Marseilles. 


Thetis 






Paris. 








London. 










Massilia 

Lutetia 

Calliope 

Thalia 


280^449,670 

232,829,135 
242,468,785 
243,206,650 
244,818,565 
253,728,615 
262,964,845 
263,421,510 
299,255,700 


1,879 

1,401 
1,518 
1,492 
1,511 
1,594 
1,682 
1,636 
2,042 


April 5, 1853 
May 5, 1853 
July 1, 1847 
May 13, 1850 
May 20, 1850 
Nov. 2, 1850 
Dec. 8, 1845 
Sept. 1, 1804 
Jan. 1, 1801 
March 28, 1802 
April 12,1849 


Gasparis.... 

Luther 

Hencke, 

Gasparis.... 

Hind 

Gasparis — 

Hencke 

Harding.... 

Piazzi 

Olbers 

Gasparis . . . 


Naples. 
Bilk, Ger. 
Driessen. 
Naples. 


New planet 

New planet 

Hebe 


London. 
Naples. 
Driessen. 


Parthenope 


Lilienthal. 
Palermo. 




Bremen. 


Astrsea 


Naples. 



477. Periodic revolution of Pallas ? Mean distance from the Sun ? Rate of motion ? 
Diameter ? What remarkable phenomenon mentioned ? 



THE PRIMARY PLANETS JUPITER AND SATURN. 233 

CHAPTER VII. 

PRIMARY PLANETS— JUPITER AND SATURN. 

4T8. Jupiter is the largest of all the planets belonging to the 
solar system. It may be readily distinguished from the fixed 
stars, by its peculiar splendor and magnitude ; appearing to the 
naked eye almost as resplendent as Venus, although it is more 
than seven times her distance from the Sun. 

When his right ascension is less than that of the Sun, he is 
our morning star, and appears in the eastern hemisphere before 
the Sun rises ; when greater, he is our evening star, and lingers 
in the western hemisphere after the Sun sets. 

Nothing can be easier than to trace Jupiter among the con- 
stellations of the zodiac ; for in whatever constellation he is seen 
to-day, one year hence he will be seen equally advanced in the 
next constellation ; two years hence, in the next ; three years 
hence, in the next, and so on ; being just a year, at a mean rate, 
in passing over one constellation. 

The exact mean motion of Jupiter in its orbit, is about one-twelfth of a degree in a day ; 
Which amounts to only 30° 20' 32" in a year. 

For 12 years to come, he will, at a mean rate, pass through 
the constellations of the zodiac, as follows : 



1856, 


Aquarius. 


1860, 


Gemini. 


1864, Libra. 


1S57, 


Pisces. 


1861, 


Cancer. 


1865, Scorpio. 


1858, 


Aries. 


1862, 


Leo. 


1866, Sagittarius. 


1859, 


Taurus. 


1863, 


Virgo. 


1867, Capricornus. 



419. Jupiter is the next planet in the solar system above the 
asteroids, and performs his annual revolution around the Sun in 
nearly 12 of our years, at the mean distance of 495,000,000 of 
miles ; moving in his orbit at the rate of 30,000 miles an hour. 

The exact period of Jupiter's sidereal revolution is 11 years, 10 months, 17 days, 14 
hours, 21 minutes, 25 % seconds. His exact mean distance from the Sun is 495,533,837 
miles ; consequently, the exact rate of his motion in his orbit, is 29,943 miles per hour. 

480. He revolves on an axis, which is nearly perpendicular to 
the plane of his orbit, in 9 hours, 55 minutes, and 50 seconds ; 
so that his year contains 10,471 days and nights ; each about 
5 hours long. 

His form is that of an oblate spheroid, whose polar diametc 

478. Comparative size of Jupiter ? How distinguished from the fixed stars ? When 
morning star, &c. ? Is he easily traced ? 479. His position in the system? His peri- 
odic time ? Distance from the Sun ? Rate of motion ? 480. Time of diurnal revolu- 
tion ? Position of axis ? Length of his days ? Number in his year ? His form ? Cause 
of his oblateness ? Difference of equatorial and polar diameters ? The Earth ? 



234 ASTRONOMY. 

is to its equatorial, as 13 to 14. He is therefore considerably- 
more flattened at the poles than any of the other planets, except 
Saturn. This is caused by his rapid rotation on his axis ; for it 
is an universal law that the equatorial parts of every body, 
revolving on an axis, will be swollen out, in proportion to the 
density of the body, and the rapidity of its motion. 

The difference between the polar and equatorial diameters of Jupiter, exceeds 6000 
miles. The difference between the polar and equatorial diameters of the Earth, is only 
26 miles. Jupiter, even on the most careless view through a good telescope, appears to 
be oval ; the longer diameter being parallel to the direction of his belts, which are also 
parallel to the ecliptic. 

481. By this rapid whirl on its axis, his equatorial inhabitants 
are carried around at the rate of 26,554 miles an hour ; which 
is 1600 miles farther than the equatorial inhabitants of the 
Earth are carried, by its diurnal motion, in twenty-four hours. 

The true mean diameter of Jupiter is 86,255 miles ; which 
is nearly 11 times greater than the Earth's. His volume is, 
therefore, about thirteen hundred times larger than that of the 
Earth. {For magnitude as compared with that of the Earth, see 
Map I.) On account of his great distance from the Sun, the 
degree of light and heat which he receives from it is 27 times 
less than that received by the Earth. 

When Jupiter is in conjunction, he rises, sets, and comes to the meridian with the Sun ; 
but is never observed to make a transit, or pass over the Sun's disc ; when in opposition, 
he rises when the Sun sets, sets when the Sun rises, and comes to the meridian at mid- 
night, which never happens in the case of an interior planet. This proves that Jupiter 
revolves in an orbit which is exterior to that of the Earth. 

482. As the variety in the seasons of a planet, and in the 
length of its days and nights, depends upon the inclination of its 
axis to the plane of its orbit, and as the axis of Jupiter has 
little or no inclination, there can be no difference in his seasons, 
on the same parallels of latitude, nor any variation in the length 
of his days and nights. It is not to be understood, however, 
that one uniform season prevails from his equator to his poles ; 
but that the same parallels of latitude on each side of his equa- 
tor, uniformly enjoy the same season, whatever season it may be. 

About his equatorial regions there is perpetual summer ; and 
at his poles everlasting winter ; but yet equal day and equal 
night at each. This arrangement seems to have been kindly 
ordered by the beneficent Creator ; for had his axis been inclined 
to his orbit, like that of the Earth, his polar winters would have 
been alternately a dreadful night of six years' darkness. 

481. Motion at Jupiter's equator ? His mean diameter ? His volume ? Light and heat? 
Does he ever transit the Sun ? What proof that his orbit is exterior to that of the Earth ? 
482. What of the seasons of Jupiter ? What apparent manifestation of Divine Wisdom ? 



THE PRIMARY PLANETS JUPITER AND SATURN. 235 




TELESCOPIC VIEW OF JUPITER. 

483. Jupiter, when 
viewed through a 
telescope, appears to 
be surrounded by a 
number of luminous 
zones, usually termed 
belts, that frequently 
extend quite around 
him. These belts are 
parallel not only to 
each other, but, in 
general, to his equa- 
tor, which is also 
nearly parallel to the 
ecliptic. They are 
subject, however, to considerable variation, both in breath and 
number. Sometimes eight have been seen at once ; sometimes only 
one, but more usually three. Dr. Herschel once perceived his 
whole disc covered with small belts, though they are more 
usually confined to within 30° of his equator, that is, to a zone 
60° in width. 

Sometimes these belts continue for months at a time with little 
or no variation, and sometimes a new belt has been seen to form 
in a few hours. Sometimes they are interrupted in their length ; 
and at other times, they appear to spread in width, and run into 
each othej, until their breadth exceeds 5000 miles. 

484. Bright and dark spots are also frequently to be seen in 
the belts, which usually disappear with the belts themselves, 
though not always, for Cassini observed that one occupied the 
same position more than 40 years. Of the cause of these vari- 
able appearances, but little is known. They are generally sup- 
posed to be nothing more than atmospherical phenomena, resulting 
from, or combined with, the rapid motion of the planet upon its 
axis. 

Different opinions have been entertained by astronomers respecting the cause of these 
belts and spots. By some they have been regarded as clouds, or as. openings in the 
atmosphere of the planet, while others imagine that they are of a more permanent 
nature, and are the marks of great physical revolutions, which are perpetually agitating 
and changing the surface of the planet. The first of these opinions sufficiently explains 
the variations in the form and magnitude of the spots, and the parallelism of the belts. 

4S3. How does Jupiter appear through a telescope? Where are his belts usually 
seen? Their number? Are they permanent? 484. What else seen upon Jupiter's 
surface? Are they permanent? Is the cause of these phenomena well understood? 
What different opinions? 



236 



ASTRONOMY. 



The spot first observed by Cassini, in 1665, which has both disappeared and reappeared 
in the same form and position for the space of 43 years, could not possibly be occasioned 
by any atmospherical variations, but seems evidently to be connected with the surface 
of the planet. The form of the belt, according to some astronomers, may be accounted 
for by supposing that the atmosphere reflects more light than the boSy of the planet, 
and that the clouds which float in it, being thrown into parallel strata by the rapidity of 
its diurnal motion, form regular insterstiees, through which are seen its opaque body, or 
any of the permanent spots which may come within the range of the opening. 



MOONS OF JUPITER. 



TELESCOPIC VrEWS OP THE MOONS OF 
JUPITER. 



485. Jupiter is attended by four satellites or moons, 
are easily seen with a common spy- 
glass, appearing like small stars 
near the primary. (See adjoining 
cut. ) By watching them for a few 
evenings, they will be seen to change 
their places, and to occupy different 
positions. At times, only one or two 
may be seen, as the others are 
either between the observer and the 
planet, or beyoTtd the primary, or 
eclipsed by his shadow. 

486. The size of these satellites 
is about the same as our moon, 
except the second, which is a trifle 
less. The first is about the distance 
of our moon ; and the others, re- 
spectively, about two, three, and 
five times as far off. 



They 




4th. 



COMPARATIVE DISTANCES OP JUPITER'S MOONS 

3d. 2d. 1st. 




487. Their periods of revolution are from 1 day 18 hours to 
1*7 days, according to their distances. This rapid motion is 
necessary, in order to counterbalance the powerful centripetal 
force of the planet, and to keep the satellites from falling to his 
surface. 

485. How many moons has Jupiter ? How seen? Why not all seen at once ? 486. 
Their size 1 Distances ? 487. Periods of Jupiter's satellites ? Why so rapid ? 



THE PRIMARY PLANETS JUPITER AND SATURN. 237 

The magnitudes, distances, and periods of the moons of Jupiter are as follows : 

Diameter in miles. Distance. Periodic times. 

1st 2,500 259,000 1 day 18 hours. 

2d 2,068 414,000 3 " 12 « 

3d 3,377 647,000 7 " 14 " 

4th 2,890 1,164,000 17 " " 

488. The orbits of Jupiter's moons are all in or near the plane 
of his equator ; and as his orbit nearly coincides with the eclip- 
tic, and his equator with his orbit, it follows that, like our own 
moon, his satellites revolve near the plane of the ecliptic. On 
this account, they are sometimes between us and the planet, and 
sometimes beyond him, and seem to oscillate, like a pendulum, 
from their greatest elongation on one side to their greatest elon- 
gation on the other. 

489. Their direction is from west to east, or in the direction 
their primary revolves, both upon his axis and in his orbit. From 
the fact that their elongations east and west of Jupiter are nearly 
the same at every revolution, it is concluded that their orbits 
are but slightly elliptical. They are supposed to revolve on 
their respective axis, like our own satellite, the moon, once dur- 
ing every periodic revolution. 

490. As these orbits lie near the plane of the ecliptic, they 
have to pass through his broad shadow when in opposition to the 
Sun, and be totally eclipsed at every revolution. To this there 
is but one exception. As the fourth satellite departs about 3° 
from the plane of Jupiter's orbit, and is quite distant, it some- 
times passes above or below the shadow, and escapes eclipse. But 
such escapes are not frequent. 

These moons are not only often eclipsed, but they often eclipse 
Jupiter, by throwing their own dark shadows upon his disc. 
They may be seen like dark round spots traversing it from side 
to side, causing, wherever that shadow falls, an eclipse of the 
Sun. Altogether, about forty of these eclipses occur in the sys- 
tem of Jupiter every month. 

491. The immersions and emersions of Jupiter's moons have 
reference to the phenomena of their being eclipsed. Their 
entrance into the shadow is the immersion ; and their coming out 
of it the emersion. 

4SS. How are their orbits situated ? How satellites appear to move ? 4S9. Direction 
of secondaries? Form of orbits ? How ascertained? What motion on axis? 490. 
What said of eclipses ? Of fourth satellite ? Of solar eclipses upon Jupiter ? Number 
of solar and lunar? 491. What are the immersions and emersions of Jupiter's 
moons ? Are the immersions and emersions always visible from the Earth ? Why not ? 
Illustrate. 



238 ASTRONOMY. 

ECLIPSES OF JUPITER'S MOONS, EMERSIONS, ETC. 



^ A 



ff//'^^\\ 



The above is a perpendicular view of the orbits of Jupiter's satellites. His oroad 
shadow is projected in a direction opposite the Sun. At C, the second satellite is suffer- 
ing an immersion, and will soon be totally eclipsed ; while at D, the first is in the act of 
emersion, and will soon appear with its wonted brightness. The other satellites are seen 
to cast their shadows off into space, and are ready in turn to eclipse the Sun, or cut off a 
portion of his beams from the face of the primary. 

If the Earth were at A in the cut, the immersion, represented at C, would be invisible ; 
and if at B, the emersion at D could not be seen. So, also, if the Earth were exactly at 
P, neither could be seen ; as Jupiter and all his attendants would be directly beyond the 
Sun, and would be hid from our view. 

492. The system of Jupiter may be regarded as a miniature 
representation of the solar system, and as furnishing triumphant 
evidence of the truth of the Copernican theory. It may also be 
regarded as a great natural clock, keeping absolute time for the 
whole world ; as the immersions and emersions of his satellites 
furnish a uniform standard, and, like a vast chronometer hung 
up in the heavens, enable the mariner to determine his longitude 
upon the trackless deep. 

By long and careful observations upon these satellites, astronomers have been able to 
construct tables, showing the exact time when each immersion and emersion will take 
place, at Greenwich Observatory, near London. Now suppose the tables fixed the time 
for a certain satellite to be eclipsed at 12 o'clock at Greenwich, but we find it to occur at 
9 o'clock, for instance, by our local time : this wouM show that our time was three hours 
behind the time at Greenwich ; or, in other words, that we were three hours, or 45°, west 
of Greenwich. If our time was ahead of Greenwich time, it would show that we were 
east of that meridian, to the amount of 15° for every hour of variation. But this method 
of finding the longitude is less used than the "lunar method" (Art. 407), on account of 
the greater difficulty of making the necessary observations. 

493. By observations upon the eclipses of Jupiter's moons, as 
compared with the tables fixing the time of their occurrence, it 
was discovered that light had a progressive motion, at the rate 
of about 200,000 miles per second. 

This discovery may be illustrated by again referring to the preceding cut. In the year 
16T5, it was observed by Roemer, a Danish astronomer, that when the Earth was nearest 
to Jupiter, as at E, the eclipses of his satellites took place 8 minutes 13 seconds sooner 
than the mean time of the tables; but wben the earth was farthest from Jupiter, as at 
F, the eclipses took place S minutes and 13 seconds later than the tables predicted, the 
entire difference being 16 minutes and 26 seconds. This difference of time he ascribed to 
the progressive motion of light, which he concluded required 16 minutes and 26 seconds 
to cross the earth's orbit from E to F. 

492. How may the system of Jupiter be regarded ? What use of it made in navigation ? 
Illustrate method? Is it much used ? 493. What discovery by observing the eclipses 
of Jupiter's moons? Explain the process? 



THE PRIMARY PLANETS JUPITER AND SATURN. 239 

This progress may be demonstrated as follows : — 16m. 26s.=986s. If the radius of the 
Earth's orbit be 95,000,000 of miles, the diameter must be twice that, or 190,000,000. 
Divide 190,000,000 miles by 986 seconds, and we have 192,697||-|- miles as the progress 
of light in each second. At this rate, light would pass nearly eight times around the globe 
at every tick of the clock, or nearly 500 times every minute ! 

494. Jupiter, when seen from his nearest satellite, appears a 
thousand times larger than our Moon does to us, exhibiting on a 
scale of inconceivable magnificence, the varying forms of a cres- 
cent, a half moon, a gibbous phase, and a fall moon, every 42 
hours. 

SATUKJN. 

495. Saturn is situated between the orbits of Jupiter and 
Uranus, and is distinctly visible to the naked eye. It may be 
easily distinguished from the fixed stars by its pale, feeble, and 
steady light. It resembles the star Fomalhaut, both in color 
and size, differing from it only in the steadiness and uniformity 
of its light. 

From the slowness of its motion in its orbit, the pupil throughout the period of his 
whole life, may trace its apparent course among the stars, without any danger of mis- 
take. Having once found when it enters a particular constellation, he may easily remem- 
ber where he is to look for it in any subsequent year ; because, at a mean rate, it is just 
23^ years in passing over a single sign or constellation. 

Saturn's mean daily motion among the stars is only about 2', 
the thirtieth 'part of a degree. 

496. The mean distance of Saturn from the Sun is nearly 
double that of Jupiter, being about 909,000,000 of miles. His 
diameter is about 82,000 miles ; his volume, therefore, is eleven 
hundred times greater than the Earth's. Moving in his orbit at 
the rate of 22,000 miles an hour, he requires 29-§- years to com- 
plete his circuit around the Sun : but his diurnal rotation on his 
axis is accomplished in 10|- hours. His year, therefore, is nearly 
thirty times as long as ours, while his day is shorter by more 
than one-half. His year contains about 25,150 of its own days, 
which are equal to 10,759 of our days. 

497. The surface of Saturn, like that of Jupiter, is diversified 
with belts and dark spots. Dr. Herschel sometimes perceived 
five belts on his surface ; three of which were dark and two 
bright. The dark belts have a yellowish tinge, and generally 
cover a broader zone of the planet than those of Jupiter. 

To the inhabitants of Saturn, the Sun appears 90 times less than he appears at the 
Earth ; and they receive from him only one nineUeth part as much light and heat. But 

494. How does Jupiter appear from his nearest satellite ? 495. Situation of Saturn ? 
How distinguished? How trace? His rate of motion in the heavens ? 496. Distance 
from the Sun? Diameter? Volume? Rate of motion in orbit ? Periodic time ? Diur- 
nal revolution? Days in his year? 497. Appearance of his surface? Belts 1 The 
Sun as seen from Saturn? Light and heat of that planet? Estimated strength of the 



240 



ASTRONOMY. 




it is computed that even the ninetieth part of the Sun's light exceeds the illuminating 
power of 3000 full moons, which would be abundantly sufficient for all the purposes of 
life. 

498. The telescopic appearance of Saturn is unparalleled. It 
is even more interesting than Jupiter, with all his moons and 
belts. That which eminently distinguishes this planet from 
every other in the system, is a magnificent zone or ring, encir- 
cling it with perpetual light. 

The adjoining out is an excel- telescopic- view of saturn. 

lent representation of Saturn 
as seen through a telescope. 
The oblateness of the planet is 
easily perceptible, and his 
shadow can be seen upon the 
rings back of the planet. The 
shadow of the rings may also 
be seen running across his disc. 
The writer has often seen the 
opening between the body of 
the planet and the interior 
ring as distinctly as it appears 
to the student in the cut. Un- 
der very powerful telescopes, 
these rings are found to be 
again subdivided into an in- 
definite number of concentric circles, one within the other, though this is considered 
doubtful by Sir John Herschel. 

499. The light of the ring is more brilliant than the planet 
itself. It turns around its center of motion in the same time 
that Saturn turns on its axis. When viewed with a good 
telescope, it is usually found to consist of two concentric rings, 
divided by a dark band. 

It has been ascertained, however, that these rings are again subdivided; the third 
division was distinctly seen by Prof. Encke, on the 25th of April, 1SS7, and also by Mr. 
Lassel, on the 7th of September, 1843, at his observatory near Liverpool, England. Six 
different rings were seen at Rome, in Italy, on~the night of the 29th of May, 1838. And 
more recent observations by Professor Bond, of Cambridge, have led to the conclusion 
that, in all probability, these wonderful rings are fluid I It is well known that under the 
most powerful instruments they seem to be almost indefinitely subdivided. 

500. As our view of the rings of Saturn is generally an 
oblique one, they usually appear elliptical, and never circular. 
The ellipse seems to contract for about T-J years, till it almost 
entirely disappears, when it begins to expand again, and con- 
tinues to enlarge for 7-J- years, when it reaches its maximum of 
expansion, and again begins to contract. For fifteen years, the 
part of the rings toward us seems to be thrown up, while for the 



solar radiance? 498. Telescopic appearance of Saturn? For what distinguished? 
499. Comparative light of his rings ? Time of rotation around the planet ? How does it 
usually appear? What further discoveries ? 500. What the general apparent figure 
of the rings? Why elliptical ? What periodic variation of expansion ? Of inclination ? 
When nearly invisible ? 



THE PRIMARY PLANETS JUPITER AND SATURN. 241 

next fifteen it appears to drop below the apparent center of the 
planet ; and while shifting from one extreme to the other, the 
rings become almost invisible, appearing only as a faint line of 
light running from the planet in opposite directions. The rings 
vary also in their inclination, sometimes dipping to the right, 
and at others to the left. 



TELESCOPIC PHASES OF THE KINGS OP SATURN. 




The above i3 a good representation of the various inclinations and degrees of expan- 
sion of the riDgs of Saturn, during his periodic journey of 30 years 



PERPENDICULAR VIEW OF THE RINGS OF SATURN. 



501. The rings of the 
planet are always directed 
more or less toward the 
Earth, and sometimes ex- 
actly toward us ; so that 
we never see them perpen- 
dicularly, but always either 
exactly edgewise, or ob- 
liquely, as shown in the last 
figure. Were either pole 
of the planet exactly toward 
us, we should then have a 
perpendicular view of the 
rings, as shown in the ad- 
joining cut. 

502. The various phases of Saturn's rings are explained by 
the facts that his axis remains parallel to itself (see following 
cut), with an uniform inclination to the plane of his orbit, which 
is very near the ecliptic ; and as the rings revolve over his 
equator, and at right angles with his axis, they also remain 
parallel to themselves. The revolution of the planet about the 
Earth every 30 years, must therefore bring first one side of the 
rings to view, and then the other — causing all the variations of 
expansion, position, and inclination which the rings present. 




501. How are the rings situated with respect to the Earth? How would they appear if 
either pole of Saturn were toward us ? 502. How are the various phases of Saturn's 
rings accounted for? 



242 



ASTRONOMY. 



SATURN AT DIFFEHEST POINTS IN HIS ORBIT. 







Here observe, first, that the axis of Saturn, like those of all the other planets, remains 
permanent, or parallel with itself; and as the rings are in the plane of his equator, and 
at right angles with his axis, they also must remain parallel to themselves, whatever 
position the planet may occupy in its orbit. 

This being the case, it is obvious that while the planet is passing from A to E, the Sun 
will shine upon the under or south, side of the rings ; and while he passes from E to A 
again, upon the topper or north side; and as it requires about 30 years for the planet 
to traverse these two semicircles, it is plain that the alternate day and night on the rings 
will be 15 years each. 

A and E are the equinoctial, and C and G- the solstitial points in the orbit of Saturn. - 
At A and E the rings are edgewise toward the Sun, and also toward the Earth, provided 
Saturn is in opposition to the Sun. To an observer on the Earth, the rings will seem to 
expand from A to C, and to contract from C to E. So, also, from E to G-, and from G to 
A. Again : from A to E the front of the rings will appear above the planet's center, and 
from E to A below it. 

The rings of Saturn were invisible, as rings, from the 22d of April, 1848, to the 19th of 
January, 1849. He came to his equinox September 7, 1848 ; from which time to February, 
1856, his rings will continue to expand. From that time to June, 1863, they will contract, 
when he will reach his other equinox at E, and the rings will be invisible. From June, 
1863, to September, 1ST0, they will again expand ; and from September, 1870, to March, 
1877, they will contract, when he will be at the equinox passed September 7, 1848, or 
29% years before. 

The writer has often seen the rings of Saturn in different stages of expansion, and con- 
traction, and once when they were almost directly edgewise toward the Earth. At that 
time (January, 1849), they appeared as a bright line of light, as represented at A and 
E, in the first cut on the preceding page. 

503. The dimensions of the rings of Saturn may be stated in 
round numbers as- v follows : 

Miles. 

Distance from the body of the planet to the first 

ring 19,000 

Width of interior ring 1*7,000 

Space between the interior and exterior rings . . 2,000 

Width of exterior ring 10,500 

Thickness of the rings 100 



503. State the distances and dimensions of his rings, beginning at the body of the plane!., 
and passing outward? What additional statistics from Herschel? 



THE PRIMARY PLANETS JUPITER AND SATURN. 243 

In a recent work, entitled " The New Theory of Creation and Deluge," it is predicted 
that, at some future time, the fluid rings of Saturn may descend and deluge the planet, 
as ours was deluged in the days of Noah. Sir David Brewster says : — " Mr. Otto Struve 
and Mr. Bond have lately studied with the great Munich telescope at the Observatory 
of Pulicoway, the third ring of Saturn, which Mr. Dassels and Mr. Bond discovered to 
be fluid. These astronomers are of opinion that this fluid ring is not of very recent 
formation, and that it is not subject to rapid change , and they have come to the extra- 
ordinary conclusion that the inner border of the ring has, since the time of Huygens, 
been gradually approaching the body of Saturn, and that we may expect, sooner or 
later, perhaps in some dozen of years, to see the rings united with the body of the planet." 

504. The rings of Saturn serve as reflectors to reflect the 
light of the Sun upon his disc, as our" Moon reflects the light to 
the Earth. In his nocturnal sky, they must appear like two 
gorgeous arches of light, bright as 
the full moon, and spanning the 
whole heavens like a stupendous 
rainbow. 



NIGHT SCBNE UPON SATURN. 




In the annexed cut, the beholder is supposed 
to be situated some 30° north of the equator of 
Saturn, and looking directly south. The shadow 
of the planet is seen travelling up the arch as 
the night advances, while a New Moon is shown 
in the west, and a Full Moon in the east at the 
same time. 

505. The two rings united are nearly 13 times as wide as the 
diameter of the Moon ; and the nearest is only y^th as far from 
the planet as the Moon is from us. 

The two rings united are 27,500 miles wide ; which -r- 21 60 the moon's diameter =12_7_ 
So 240,000 miles, the Moon's distance -*- 19,000 the distance of Saturn's interior 
ring=12 T f. 

At the distance of only 19,000 miles, our Moon would appear some forty times as large 
as she does at her present distance. How magnificent and inconceivably grand, then, 
must these vast rings, appear, with a thousand times the Moon's magnitude, and only 
one-twelfth part of her distance ! 

506. The periodic time of Saturn being nearly thirty years, 
his motion eastward among the stars must be very slow, amount- 
ing to only 12° a year, or one sign in 2|- years. It will be easy, 
therefore, having once ascertained his position, to watch his slow 
progress eastward year after year. Saturn is now (1855) just 
east of the seven stars. 

MOONS OF SATURN". 

501. Besides the magnificent rings already described, the 
telescope reveals eight satellites or moons, revolving around Saturn. 
But these are seen only with good instruments, and under favor- 
able circumstances. 

504. What purpose do the rings of Saturn serve? How appear in his evening sky? 
505. Width of two rings, as compared with Moon ? Distance? Demonstrate both. How 
would our Moon appear at the distance of Saturn's rings? 506. Eastward motion of 
Saturn? How traced? 507. Moons of Saturn ? How seen? Best time for observing? 

B.Gr. 11 




244 ASTRONOMY. 

SATELLITES OF SATURN. 

The best time for observ- 
ing them is when the planet 
is at his equinoxes, and his 
rings are nearly invisible. 

In January, 1849, the author saw five 
of these satellites, as represented in the adjoining cut. The rings appeared only as a line 
of light extending each way from the planet, and the satellites were in the direction of 
the line, at different distances, as here represented. 

508. These satellites all revolve eastward with the rings of 
the planet, in orbits nearly circular, and, with the exception of 
the eighth, in the plane of the rings. Their mean distances, 
respectively, from the planet's center are from 123,000 to 
2,366,000 miles ; and their periods from 22 hours to 19 days, 
according to their distances. 

The distances and periods of the satellites of Saturn are as follows : 

Distance in miles. Periodic times. Distance in miles. Periodic times. 



1st 123,000 day 22 hours 

2d 158,000 1 " 8 

3d 196,000 1 " 21 

4th 251,000 2 " 17 



5th 351,000 4 days 12 hours. 

6th 811,000 15 " 22 " 

7th 2,366,000 79 " 7 " 



Of the 8th satellite recently discovered, we have as yet much 
less knowledge than of its predecessors. 

COMPARATIVE DISTANCES OF THE MOONS OF SATURN. 



509. The most distant of these satellites is the largest, sup 
posed to be about the size of Mars ; and the remainder grow 
smaller as they are nearer the primary. They are seldom eclipsed, 
on account of the great inclination of their orbits to the ecliptic, 
except twice in thirty years, when the rings are edgewise toward 
the Sun, The eighth satellite, which has been studied more than 
all the rest, is known to revolve once upon its axis during every 
periodic revolution ; from which it is inferred that they all 
revolve on their respective axis in the same manner. 



Let the line A B represent the plane 
of the planet's orbit, C D his axis, and 
E F the plane of his rings. The satellites 
being in the plane of the rings will 
revolve around the shadow of the pri- 
mary, instead of passing through it, and 
being eclipsed. 

At the time of his equinoxes, however, 
when the rings are turned toward the 
Sun (see A and E, cut, page 242) they 
must be in the center of the shadow on 



SYSTEM OF SATURN — NO ECLIPSES. 




508. The revolutions ? Shape and position of their orbits ? Distances from their pri- 
lary? 509. Comparative size? 



THE PRIMARY PLANETS JUPITER AND SATURN. 245 

the opposite side ; and the moons, revolving in the plane of the rings, must pass through 
the shadow at every revolution. The eighth, however, may sometimes escape, on account 
of his departure from the plane of the rings, as shown in the cut. 

510. The theory of the satellites of Saturn is less perfect than 
than that of the satellites of Jupiter. The difficulty of observ- 
ing their eclipses, and of measuring their elongations from their 
primary, have prevented astronomers from determining, with 
their usual precision, their mean distances and revolutions. But 
of this we are certain : there is no planet in the solar system, 
whose firmament presents such a variety of splendid and mag- 
nificent objects as that of Saturn. 

The various aspects of the seven moons, one rising above the horizon, while another is 
setting, and a third approaching to the meridian ; one entering into an eclipse, and 
another emerging from one ; one appearing as a crescent, and another with a gibbous 
phase ; and sometimes the whole of them shining in the same hemisphere, in one bright 
assemblage ! The majestic motion of the rings — at one time illuminating the sky with 
their splendor, and eclipsing the stars ; at another, casting a deep shade over certain 
regions of the planet, and unveiling to view the wonders of the starry firmament, are 
scenes worthy of the majesty of the Divine Being to unfold, and of rational creatures to 
contemplate. 

Such displays of Wisdom and Omnipotence, lead us to conclude that the numerous 
splendid objects connected with this planet, were not created merely to shed their luster 
on naked rocks and barren sands ; but that an immense population of intelligent beings 
is placed in those regions, to enjoy the bounty, and adore the goodness, of their great 
Creator. 



CHAPTER VIII. 

PRLMAKY PLANETS.— UPvANUS AND NEPTUNE. 

511. Uranus is the next planet in order from the Sun, beyond 
or above Saturn. To the naked eye, it appears like a star of 
only the 6th or 1th magnitude, and of a pale, bluish white ; but 
it can seldom be seen, except in a very fine, clear night, and in 
the absence of the Moon. Through a telescope, he exhibits a 
small, round, uniformly illuminated disc, without rings, belts, or 
discernible spots. His apparent diameter is about 4", from 
which he never varies much, owing to the smallness of our orbit 
in comparison with his own. 

510. Is the system of Saturn well understood? Why not? Of what are we sure? 
What scenes must it present? To what conclusion must these phenomena lead us? 
511. Position and appearance of Uranus ? Through a telescope ? 



246 ASTRONOMY. 

Sir John Herschel says he is without discernible spots, and yet in his tables he lays 
down the time of the planet's rotation (which could only be ascertained by the rotation 
of spots upon the planet's disc), at 9}g hours. This time is probably given on the 
authority of Schroeter, and is marked as doubtful by Dr. Herschel. 

512. The motion of Uranus in longitude is still slower than 
that of Saturn. It moves over but one degree of its orbit in 
85 days ; hence he will be seven years in passing over one sign 
or constellation. His periodic time being 84 years 27 days, his 
eastward motion can amount to only about 4° 17' in a whole 
year. To detect this motion requires instruments and close 
observations. At this date (1855), Uranus has passed over 
about -J of his orbit, since' his discovery in 1181 ; and in 1865 
will have traversed the whole circuit of the heavens, and reached 
the point where Herschel found him 84 years before. 

It is remarkable that this body was observed as far back as 1690. It was seen three 
times by Flamstead, once by Bradley, once by Mayer, and eleven times by Lemonnier, 
who registered it among the stars ; but not one of them suspected it to be a planet. 

513. The inequalities in the motions of Jupiter and Saturn, 
which could not be accounted for from the mutual attractions 
of these planets, led astronomers to suppose that there existed 
another planet beyond the orbit of Saturn, by whose action 
these irregularities were produced. This conjecture was con- 
firmed March 13th, 1781, when Dr. Herschel discovered the 
motions of this body, and thus proved it to be a planet. 

514. The mean distance of Uranus from the Sun is 
1,828,000,000 of miles ; more than twice the mean distance of 
Saturn. His sidereal revolution is performed in 84 years and 
1 month, and his motion in his orbit is 15,600 miles an hour. 
He is supposed to have a rotation on his axis, in common with 
the other planets ; but astronomers have not yet been able to 
obtain any ocular proof of such a motion 

515. His diameter is estimated at 34,000 miles ; which would 
make his volume more than 80 times larger than the Earth's. 
To his inhabitants, the Sun appears only the ^-}j part as large 
as he does to us ; and of course they receive from him only that 
small proportion of light and heat. It may be shown, however, 
that the ^} T part of the Sun's light exceeds the illuminating 
power of 800 full moons. This, added to the light they must 
receive from their six satellites, will render their days and 
nights far from cheerless. 

512. His motion in longitude ? Periodic time ? Angular motion per year ? How far 
has he been traced since his discovery? When complete his revolution? Was he ever 
Been previous to 1781 ? By whom ? Why are they not the discoverers, then ? 513. Was 
his existence suspected previous to 1781 ? What ground for the suspicion ? How proved 
to be a planet? 514. Mean distance? Sidereal revolution? Hourly motion in orbit ? 
Rotation on axis ? 515. Diameter ? Volume? Light and heat? Use of satellites? 



THE PRIMARY PLANETS URANUS AND NEPTUNE. 247 

516. Uranus is attended by six moons or satellites, which 
revolve about him in different periods, and at various distances. 
Four of them were discovered by Sir William Herschel, and two 
by his sister, Miss Caroline Herschel. It is possible that others 
remain yet to be discovered. 

Sir William Herschel reckoned six, though no other observer has confirmed this opinion ; 
and even his son, Sir John Herschel, seems to consider the existence of six satellites quite 
doubtful. After mentioning the two most conspicuous, he says : " Of the remaining four, 
whose existence, though announced with considerable confidence by their original dis- 
coverer, could hardly be regarded as fully demonstrated, two only have been hitherto 
re-observed."— Outlines of Astronomy, Article 551. The two that he regarded as doubt- 
ful he supposed would be found, if at all, in orbits exterior to those of the other four. 

The distance from the planet and periodic times of the satellites of Uranus, respectively, 
are as follows : 

Difit. in miles. Periodic Times. Dist. in miles. Periodic Times. 

D. H. M. S. D. H. M. S. 

1 224,000 5 21 25 20 14 390,000 11 10 56 29 

2 296,000 8 16 57 47 15 777,000 38 01 48 00 

3 340,000 10 23 02 47 6 1,556,000 107 16 39 56 



NEPTUNE. 

511. This is the most distant of the primary planets, and in 
some respects one of the most interesting. It is about 31,000 miles 
in diameter, is situated at the mean distance of 2,850,000,000 
miles from the Sun, and revolves around him in 164 years. So 
remote is this newly-discovered member of the solar system, that 
for a body to reach it, moving at railroad speed, or 30 miles- an 
hour, would require more than twenty thousand years ! 

518. The circumstances of the discovery of this planet are at 
once interesting and remarkable. Such is the regularity of the 
planetary motions, that astronomers are enabled to predict, with 
great accuracy, their future places in the heavens, and to con- 
struct tables, exhibiting their positions for ages to come. Soon 
after the discovery of Uranus, in 1*181, his orbit was computed, 
and a table constructed for determining his future positions in 
the heavens, but instead of following the prescribed path, or 
occupying his estimated positions, he was found to be yielding to 
some mysterious and unaccountable influence, under which he 
was gradually leaving his computed orbit, and failing to meet 
conditions of the tables. 



516. Number of Moons ? By whom discovered ? Is it certain that Uranus has six 
satellites? "Why doubtful ? 517. Distance and diameter of Neptune? Period? How 
long to pass from the Sun to it at railroad speed ? 518. What remarkable circum- 
stances respecting its discovery? Perturbation ? 



248 ASTRONOMY. 

519. At first this discrepancy between the observed and the 
estimated places of Uranus, was charged upon the tables, and a 
new orbit and new tables were computed, which it was thought 
could not fail to represent the future places of the planet. But 
these also seemed to be erroneous, as it was soon discovered that 
the computed and observed places did not agree, and the differ- 
ence was becoming greater and greater every year. This was 
an anomaly in the movements of a planetary body. It was not 
strange that it should be subject to perturbations, from the attrac- 
tive influence of the large planets Jupiter and Saturn, as these 
were known to act upon him, as well as upon each other, and 
the smaller planets, producing perturbations in their orbits, but 
all this had been taken into the account in constructing the 
tables, and still the planet deviated from its prescribed path. 

520. To charge the discrepancy to the tables, was no longer 
reasonable, though it was thought perhaps sufficient allowance 
had not been made, in their computation, for the disturbing influ- 
ence of Jupiter and Saturn. To determine this question, M. Le- 
verrier, of Paris, undertook a thorough discussion of the sub- 
ject, and soon ascertained that the disturbing influence upon 
IJranus of all the known planets, was not sufficient to account 
for the anomalous perturbations already described, and that they 
were probably caused by some unknown planet, revolving beyond 
the orbit of IJranus. From the amount and effect of this dis- 
turbing influence from an unknown source, the distance, magni- 
tude, and position of the imaginary planet were computed. 

521. At this stage of the investigation, Leverrier wrote to 
his friend, Dr. G-alle, of Berlin, requesting him to direct his 
telescope to that part of the heavens in which his calculations 
had located the new planet, when lo ! there he lay, a thousand 
millions of miles beyond the orbit of Uranus, and yet within less 
than one degree of the place pointed out by Leverrier ! This 
was on the 1st of September, 1846. 

522. While M. Leverrier was engaged in his calculations at 
Paris, Mr. Adams, a young mathematician of Cambridge, Eng- 
land, was discussing the same great problem, and had arrived at 
similar results even before M. Leverrier, though entirely igno- 
rant of each other's labors or conclusions. This seems to estab- 



519. To what attributed at first? What done to correct? What then? 520. What 
next undertaken, and by whom ? What result and conclusion? 521. What remarkable 
computation and letter ? Result of Dr. G-alle's search ? 522. Who else investigating 
the subject at the same time? His conclusions? What fact does this establish? Why 
not Adams the discoverer ? 



THE PRIMARY STARS SATURN AND NEPTUNE. 249 

lish the fact, that the new planet was discovered by calculation, 
though the failure of Mr. Adams to publish his conclusions, cut 
off his right to the honor of the discovery. 

523. Since the discovery of this planet, it has been ascertained 
that it was seen as far back as 1795, though supposed to be a 
fixed star, and catalogued as such ; and that all the irregulari- 
ties of Uranus, with which astronomers were so much perplexed, 
are perfectly accounted for by the influence of the new planet. 

524. On the 12th of October, 1846, Mr. Lassell, of Starfield, 
near Liverpool, discovered a satellite attendant upon Leverrier, 
and also, as he supposes, one or more tings similar to those of 
Saturn ; but though the secondary has often been seen by others 
since, and has been made the basis of elaborate calculations 
respecting the mass of the primary, no further discovery of the 
rings has been made by any other observer. 



CHAPTER IX. 

COMETS— THEIR NATURE, MOTIONS, ORBITS, &o. 

525. Comets, whether viewed as ephemeral meteors, or as 
substantial bodies, forming a part of the solar system, are objects 
of no ordinary interest. When, with uninstructed gaze, we look 
upwards, to the clear sky of evening, and behold, among the 
multitudes of heavenly bodies, one, blazing with its long train 
of light, and rushing onward towards the center of our system, 
we insensibly shrink back as if in the presence of a supernatural 
being. But when, with the eye of astronomy, we follow it 
through its perihelion, and trace it far off, beyond the utmost 
verge of the solar system, till it is lost in the infinity of space, 
not to return for centuries, we are deeply impressed with a sense 
of that power which could create and set in motion such 
bodies. 

526. Comets are distinguished from the other heavenly bodies, 
by their appearance and motion. The appearance of the planets 

523. Has Neptune ever been seen prior to 1846? What supposed to be? Does it 
account for the perturbation of Uranus? 5*24. Has Neptune a satellite? When, and 
by whom discovered? What said of rings t 525. Subject of this chapter? How 
comets regarded by the uninstructed? By the astronomer? 526. How distinguished 



250 ASTRONOMY. 

is globular, and their motion around the Sun is nearly in the 
same plane, and from west to east ; but the comets have a 
variety of forms, and their orbits are not confined to any par- 
ticular part of the heavens ; nor do they observe any one general 
direction. 

The orbits of the planets approach nearly to circles, while 
those of the comets are very elongated ellipses. A wire hoop, 
for example, will represent the orbit of a planet. If two oppo- 
site sides of the same hoop be extended, so that it shall be long 
and narrow it will then represent the orbit of a comet. The 
Sun is always in one of the foci of the comet's orbit. 

ORBIT OF A COMET. 




Here it will be seen that the orbit is very eccentric, that the perihelion point is very 
near the Sun, and the aphelion point very remote. 

There is, however, a practical difficulty of a peculiar nature which embarrasses the 
solution of the question as to the form of the cometary orbits. It so happens that the 
only part of the course of a comet which can ever be visible, is a portion throughout 
which the ellipse, the parabola, and hyperbola, so clos.ely resemble each other, that no 
observations can be obtained with sufficient accuracy to enable us to distinguish them. 
In fact, the observed path of any comet, while visible, may belong either to an ellipse', 
parabola, or hyperbola. 

52't. That part which is usually brighter, or more opaque, than 
the other portions of the comet, is called the nucleus. This is 
surrounded by an envelope, which has a cloudy, or hairy appear- 
ance. These two parts constitute the body, and, in many 
instances, the whole of the comet. Most of them, however, are 
attended by a long train, called the tail • though some are with- 
out this appendage, and as seen by the naked eye, are not easily 
distinguished from the planets. Others again, have no apparent 
nucleus, and seem to be only globular masses of vapor. 

Nothing is known with certainty of the composition of these bodies. The envelope 
appears to be nothing more than vapor, becoming more luminous and transparent when 

from other bodies? Form? Orbits? What practical difficulty mentioned? 527. 
What is the nucleus of a comet? The envelope ? The tail? Have all comets these 
three parts? Do we understand of what they are composed? What evidence of their 
extreme tenuity? 



COMETS THEIR NATURE, MOTIONS, ORBITS, ETC. 251 

approaching the Sun. As the comet3 pass between us and the fixed stars, their envelopes 
and tails are so thin, that stars of very small magnitude may be seen through them. 
Some comets, having no nucleus, are transparent throughout their whole extent. 

528. The nucleus of a comet sometimes appears opaque, and 
it then resembles a planet. Astronomers, however, are not 
agreed upon this point. Some affirm that the nucleus is always 
transparent, and that comets are in fact nothing but a mass of 
vapor, more or less condensed at the center. By others it is main- 
tained that the ^nucleus is sometimes solid and opaque. It 
seems probable, however, that there are three classes of comets, 
viz. ; 1st. Those which have no nucleus, being transparent 
throughout their whole extent ; 2d. Those which have a trans- 
parent nucleus ; and, 3d. Those having a nucleus which is solid 
and opaque. 

529. A comet, when at a distance from the Sun, viewed 
through a good telescope, has the appearance of a dense vapor 
surrounding the nucleus, and sometimes flowing far into the 
regions of space. As it approaches the Sun, its light becomes 
more brilliant, till it reaches its perihelion, when its light is more 
dazzling than that of any other celestial body, the Sun excepted. 
In this part of its orbit are seen to the best advantage the phe- 
nomena of this wonderful body, which has, from remote antiquity, 
been the specter of alarm and terror. 

530. The luminous train of a comet usually follows it, as it 
approaches the Sun, and goes before it, when the comet recedes 
from the Sun ; sometimes the tail is considerably curved towards 
the region to which the comet is tending, and in some instances, 
it has been observed to form a right angle with a 'line drawn 
from the Sun through the center of the comet. The tail of the 
comet of 1744, formed nearly a quarter of a circle ; that of 
1689 was curved like a Turkish sabre. (Map IX., Fig. 13.) 
Sometimes the same comet has several tails. That of 1144 had, 
at one time, no less than six, which appeared and disappeared in 
a few days. (See Map IX., Fig. 74.) The comet of 1823 
had, for several days, two tails ; one extending towards the Sun, 
and the other in the opposite direction. 

531. Comets, in passing among and near the planets, are ma- 
terially drawn aside from their courses, and in some cases have 
their orbits entirely changed. This is remarkably true in regard 

528. What difference of opinion respecting the nucleus of comets ? What probable 
solution ? 529. How do they appear when viewed through a telescope at a distance 
from the Sun ? As it approaches him ? Where seen to best advantage ? 530. Usual 
direction of the trains of comets? Other positions? Comet of 1744? Of 1689? Of 
1S23? 531. Influence of attraction upon comets? Illustrations ? Comet of 1770 ? 

11* 



252 ASTRONOMY. 

to Jupiter, which seems by some strange fatality to be constantly 
in their way, and to serve as a perpetual stumbling-block to 
them. 

" The remarkable comet of 1770, which was found by Lexell to revolve in a moderate 
ellipse, in a period of about five years, actually got entangled among the satellites of 
Jupiter, and thrown out of its orbit by the attractions of that planet," and has not been 
heard of since.— Herschel, p. 310. By this extraordinary rencontre, the motions of 
Jupiter's satellites suffered not the least perceptible derangement; a sufficient proof of 
the aeriform nature of the comet's mass. 

532. It is clear from observation, that comets contain very 
little matter. For they produce little or no effect on the motion 
of the planets when passing near those bodies ; it is said that a 
comet, in 1454, eclipsed the Moon ; so that it must have beeD 
very near the Earth ; yet no sensible effect was observed to be 
produced by this cause, upon the motion of the Earth or the 
Moon. 

The observations of philosophers upon comets, have as yet detected nothing of their 
nature. Tycho Brahe and Appian supposed their tails to be produced by the rays of the 
Sun transmitted through the nucleus, which they supposed to be transparent, and to ope- 
rate as a lens. Kepler thought they were occasioned by the atmosphere of the comet, 
driven off by the impulse of the Sun's rays. This opinion, with some modification, was 
also maintained by Buler. Sir Isaac Newton conjectured that they were a thin vapor, 
rising from the heated nucleus, as smoke ascends from the Earth; while Dr. Hamilton 
supposed them to be streams of electricity. 

" That the luminous part of a comet," says Sir John Herschel, " is something in the 
nature of a smoke, fog, or cloud, suspended in a transparent atmosphere, is evident from 
a fact which has been often noticed — viz., that the portion of the tail where it comes up 
to, and surrounds the head, is yet separated from it by an interval less luminous ; as we 
often'see one layer of clouds laid over another with a considerable clear space between 
them." And again : " It follows that these can only be regarded as great masses of thin 
vapor, susceptible of being penetrated through their whole substance by the sunbeams." 

533. Comets have always been considered by the ignorant and 
superstitious, as the harbingers of war, pestilence, and famine. 
Nor has this opinion been, even to this day, confined to the 
unlearned. It was once universal. Aud when we examine the 
dimensions and appearances of some of these bodies, we cease 
to wonder that they produced universal alarm. 

According to the testimony of the early writers, a comet which could be seen in day- 
light with the naked eye, made its appearance 43 years before the birth of our Saviour. 
This date was just after the death of Cassar, and by the Romans, the comet was believed 
to be his metamorphosed soul, armed with fire and vengeance. This comet is again men- 
tioned as appearing in 1106, and then resembling the Sun in brightness, being of a great 
size, and having an immense tail. In the year 1402, a comet was seen, so brilliant as to 
be discerned at noon-day. 

534. In 1456, a large comet made its appearance. It spread 
a wider terror than was ever known before. The belief was very 
general, among all classes, that the comet would destroy the 
Earth, and that the Day of Judgment was at hand ! 

532. What said of their physical natures ? Opinion of Tycho Brahe ? Of Kepler and 
Euler ? Of Newton and Dr. Hamilton ? Of Sir John Herschel ? 533. How have comets 
usually been regarded by the ignorant? What remarkable comet mentioned? 534. 
What comet in 1456 ? Effect of its appearance ? Has it appeared since ? Its period ? 



COMETS THEIR NATURE, MOTIONS, ORBITS, ETC. 253 

The same comet appeared again in the years 1531, 1607, 1682, 
1758 and 1835. It passed its perihelion in November, 1835, 
and will re-appear every T5-J- years thereafter. 

At the time of the appearance of this comet, the Turks extended their victorious arms 
across the Hellespont, and seemed destined to overrun all Europe. This added not a 
little to the general gloom. Under all these impressions, the people seemed totally regard- 
less of the present, and anxious only for the future. The Romish Church held at this 
time unbounded sway over the lives, and fortunes, and consciences of men. To prepare 
the world for its expected doom, Pope Calixtus III. ordered the Ave Maria to be repeated 
three times a day, instead of two. He ordered the church bells to be rung at noon, 
which was the origin of that practice, so universal in Christian churches. To the Ave 
Maria, the prayer was added — " Lord ! save us from the Devil, the Turk and the Comet ;" 
and once, each day, these three obnoxious personages suffered a regular excommuni- 
cation. 

The Pope and clergy exhibiting such fear, it is not a matter of wonder that it became 
the ruling passion of the multitude. The churches and convents were crowded for con- 
fession of sins ; and treasures uncounted were poured into the Apostolic chamber. 

The comet, after suffering some months of daily cursing and excommunication, began 
to show signs of retreat, and soon disappeared from those eyes in which it found no 
favor. Joy and tranquillity soon returned to the faithful subjects of the Pope, but not so 
their money and lands. The people, however, became satisfied that their lives, and the 
safety of the world, had been cheaply purchased. The Pope, who had achieved so signal 
a victory over the monster of the sky, had checked the progress of the Turk, and kept, 
for the present, his Satanic majesty at a safe distance ; while the Church of Rome, 
retaining her unbounded wealth, was enabled to continue that influence over her follow- 
ers, which she retains, in part, to this day. 

535. The comet of 1680 would have been still more alarming 
than that of 1456,. had not science robbed it of its terrors, and 
history pointed to the signal failure of its predecessor. This 
comet was of the largest size, and had a tail whose enormous 
length was more than ninety-six millions of miles. (Map IX., 
Fig. 15.) 

At its greatest distance, it is 13,000,000,000 of miles from 
the Sun ; and at its nearest approach, only 574,000 miles from 
his center ;* or about 130,000 miles from his surface. In that 

* In Brewster's edition of Ferguson, this distance is stated as only 49,000 miles. This 
is evidently a mistake ; for if the comet approached the Sun's center within 49,000 miles, 
it would penetrate 390,000 miles below the surface ! Taking Ferguson's own elements for 
computing the perihelion distance, the result will be 494,460 miles. The mistake may be 
accounted for, by supposing that the cypher had been omitted in the copy, and the period 
pointed off one figure farther to the left. Yet, with this alteration, it would be still incor- 
rect ; because the Earth's mean distance from the Sun, which is the integer of this calcu- 
lation, is assumed at 82,000,000 of miles. The ratio of the comet's perihelion distance 
from the Sun, to the Earth's mean distance, as given by M. Pingre, is as 0.00603 to 1. 
This multiplied into 95,273,869, gives 514,500 miles for the comet's perihelion distance 
from the Sun's center ; from which, if we substract his semi-diameter, 443,840 miles, we 
shall have 130,660 miles, the distance of the comet from the surface of the Sun. 

Again, if we divide the Earth's mean distance from the Sun, by the comet's perihelion 
distance, we shall find that the latter is only l-166th part of the Earth's distance. Now 
the square of 166 is 27,556 ; and this expresses the number of times that the Sun appears 
larger to the comet, in the above situation, than it does to the Earth." Squire makes it 
34,596 times larger. 

According to Newton, the velocity is 880,000 miles per hour. More recent discoveries 
indicate a velocity of 1,240,108 miles per hour. 

Incidents respecting the Turks and Church of Rome ? 535. Comet of 1630 ? Length of 
its tail? Aphelion and perihelion distances? Rapidity of its motion when nearest the Sun ? 
What error corrected ? Appearance of the Sun from that point? Heat of the comet? 
Indicates what? Fanciful theory of Dr. Whiston, and remarks upon it ? 



254 ASTRONOMY. 

part of its orbit which is nearest the Sun, it flies with the amaz- 
ing swiftness of 1,000,000 miles in an hour, and the Sun, as seen 
from it, appears 21,000 times larger than it appears to us ; con- 
sequently, it is then exposed to a heat 2*1,000 times greater than 
the solar heat at the Earth. This intensity of heat exceeds, 
several thousand times, that of red-hot iron, and indeed all the 
degrees of heat that we are able to produce. A simple mass of 
vapor, exposed to a thousandth part of such a heat, would be 
at once dissipated in space — a pretty strong indication that, 
however volatile are the elements of which comets are composed, 
they are, nevertheless, capable of enduring an inconceivable 
intensity of both heat and cold. 

This is the comet which, according to the reveries of Dr. Whiston and others, deluged 
the world in the time of Noah. Whiston was the friend and successor of Newton ; but, 
anxious to know more than is revealed, he passed the bounds of sober philosophy, and 
presumed not only to fix the residence of the damned, but also the nature of their punish- 
ment. According to this theory, a comet was the awful prison-house in which, as it 
wheeled from the remotest regions of darkness and cold into the very vicinity of the 
Sun, hurrying its wretched tenants to the extremes of perishing cold and devouring fire, 
the Almighty was to dispense the severities of his justice. Such theories may be ingenious, 
but they have no basis of facts to rest upon. They more properly belong to the chimeras 
of Astrology, than to the science of Astronomy. 

536. When we are told by philosophers of great caution and 
high reputation, that the fiery train of the comet, just alluded 
to, extended from the horizon to the zenith ; and that that of 
1144 had, at one time, six tails, each 6,000,000 of miles long, 
long, and that another, which appeared soon after, had one 
40,000,000 of miles long, and when we consider also the incon- 
ceivable velocity with which they speed their flight through the 
solar system, we may cease to wonder if, in the darker ages, 
they have been regarded as evil omens. 

But these idle fantasies are not peculiar to any age or country. Even in our own 
tirnes, the beautiful comet of 1811, the most splendid one of modern times, was generally 
considered among the superstitious, as the dread harbinger of the war which was 
declared in the following spring. It is well known that an indefinite apprehension of a 
more dreadful catastrophe lately pervaded both continents, in anticipation of Biela's 
comet of 1S32. 

531. The nucleus of the comet of 1811, according to observa- 
tions made near Boston, was 2611 miles in diameter, correspond- 
ing nearly to the size of the Moon. The brilliancy with which 
it shone, was equal to one-tenth of that of the Moon. The 
envelope, or aeriform covering surrounding the nucleus, was 
24,000 miles thick, about five hundred times as thick as the 
atmosphere which encircles the Earth ; making the diameter of 
comet, including its envelope, 50,611 miles. It had a very 

536. Why not strange that these comets were regarded as evil omens ? Are such super- 
stitions peculiar to any age or country ? What illustrations? 537. Size of the comet 
of 1811? Its motion at its perihelion ? 



COMETS THEIR NATURE, MOTIONS, ORBITS, ETC, 255 

luminous tail, whose greatest length was one hundred millions of 
miles. Map IX., Fig. 76. This comet moved, in its perihelion, 
with an almost inconceivable velocity — fifteen hundred times 
greater than tha£ of a ball bursting from the mouth of a cannon. 

538. According to Regiomontanus, the comet of 1472 moved 
over an arc of 120° in one day. Brydone observed a comet at 
Palermo in 1710, which passed through 50° of a great circle in 
the heavens in 24 hours. Another comet, which appeared in 
1759, passed over 41° in the same time. The conjecture of Dr. 
Halley, therefore, seems highly probable, that if a body of such a 
size, having any considerable density, and moving with such a 
velocity, were to strike our Earth, it would instantly reduce it 
to chaos, mingling its elements in ruin. 

The transient effect of a body passing near the Earth, could scarcely amount to any 
great convulsion, says Dr. Brewster ; but if the Earth were actually to receive a shock 
from one of these bodies, " having any considerable density," the consequences would 
indeed be awful. A new direction would be given to its rotary motion, and it would 
revolve around a new axis. The seas, forsaking their beds, would be hurried, by their 
centrifugal force, to the new equatorial regions; islands and continents, the abodes of 
men and animals, would be covered by the universal rush of the waters to the new 
equator, and every vestige of human industry and genius would be at once destroyed. 
But so far as we are as yet acquainted with these singular bodies, they are altogether too 
light and gasseous to produce any such results by collision. 

539. The chances against such an event, however, are so very 
numerous, that there is no reason to dread its occurrence. The 
French government, not long since, called the attention of some 
of her ablest mathematicians and astronomers to the solution of 
this problem ; that is, to determine upon mathematical principles, 
how many chances of collision the Earth was exposed to. After a 
mature examination, they reported — " We have found that, of 
281,000,000 of chances, there is only one unfavorable — there ex- 
ists but one which can produce a collision between the two bodies." 

" Admitting, then," say they, " for a moment, that the comets which may strike the 
Earth with their nucleuses, would annihilate the whole human race ; the danger of death 
to each individual, resulting from the appearance of an unknown comet, would be 
exactly equal to the risk he would run, if in an urn there was only one single white ball 
among a total number of 231,900,000 balls, and that his condemnation to death would be 
the inevitable consequence of the white ball being produced at the first drawing." 

A little reflection, however, will show that all such fears are groundless. The same 
unerring hand that guides the ponderous planet in its way, directs also the majestic 
comet ; and where infinite wisdom and almighty power direct, it is almost profane to talk 
of collision or accident. 

540. We have before stated that comets, unlike the planets, 
observe no one direction in their orbits, but approach to, and 
recede from their great center of attraction, in every possible 

538. Velocity of the comet of 1472? Of 1T70? Of 1759? Dr. Halley's conjecture? 
Dr. Brewster's ? Could a comet produce any such effects ? 539. Is such a collision 
probable? Why not? 540. What said of the orbits of comets and their various 
directions ? 



256 ASTRONOMY. 

direction. Nothing can be more sublime, or better calculated to 
fill the mind with profound astonishment, than to contemplate the 
revolution of comets, while in that part of their orbits which 
comes within the sphere of the telescope. Sojne seem to come 
up from the immeasurable depths below the ecliptic, and, having 
doubled the heavens' mighty cape, again plunge downward with 
their fiery trains, 

" On the long travel of a thousand years." 

Others appear to come down from the zenith of the universe 
to double their perihelion about the Sun, and then reascend far 
above all human vision. Others are dashing through the solar 
system in all possible directions, and apparently without any 
undisturbed or undisturbing path prescribed by Him who guides 
and sustains them all. 

541. Until within a few years, it was universally believed that 
the periods of their revolutions must necessarily be of prodigious 
length ; but within a few years, two comets have been discov- 
ered, whose revolutions are performed, comparatively, within 
our own neighborhood. To distinguish them from the more 
remote, they are denominated the Comets of a short period. The 
first was discovered in the constellation Aquarius, by two French 
astronomers, in the year 1786. The same comet was again 
observed by Miss Caroline Herschel, in the constellation Cygnus, 
in 1795, and again in 1805. In 1818, Professor Encke deter- 
mined the dimensions of its orbit, and the period of its sidereal 
revolution ; for which reason it has been called " Encke' 's Comet." 
Map IX., Fig. 11. 

This comet performs its revolution around the Sun in about 3 years and 4 months, in 
an elliptical orbit which lies wholly within the orbit of Jupiter. Its mean distance from 
the Sun is 212,000,000 of miles; the eccentricity of its orbit is 179,000,000 of miles; con- 
sequently, is 358,000,000 of miles nearer the Sun in its perihelion, than it is in its aphe- 
lion. It was visible throughout the United States in 1S25, when it presented a fine 
appearance. It was also observed at its next return in 182S ; but its return to its perihe- 
lion on the 6th of May, 1S32, was invisible in the United States, on account of its great 
southern declination. It has returned at regular periods since that time. 

542. The second " comet of a short period," was observed in 
1TT2 ; and was seen again in 1805. It was not until its reap- 
pearance in 1826, that astronomers were able to determine the 
elements of its orbit, and the exact period of its revolution. 
This was successfully accomplished by M. Biela of Josephstadt ; 
hence it is called Biela? s Comet. 

541. What opinion respecting their periods? What distinction in comets founded on 
the lengths of their periods? History of " Encke 1 's Comet?" Its period, orbit, mean 
distance, eccentricity of its orbit? 542. History of " Biela's Comet? 1 '' Its diameter? 



COMETS THEIR NATURE, MOTIONS, ORBITS, ETC. 257 

According to observations made upon it in 1805, by the celebrated Dr. Olbers, its 
diameter, including its envelope, is 42,280 miles. It is a curious fact, that the path of 
Biela's Comet passes very near to that of the Earth ; so near, that at the moment the 
center of the comet is at the point nearest to the Earth's path, the matter of the comet 
extends beyond that path, and includes a portion within it. Thus, if the Earth were at 
that point of its orbit which is nearest to the path of the comet, at the same moment 
that the comet should be at that point of its orbit which is nearest to the path of the 
Earth, the Earth would be enveloped in the nebulous atmosphere of the comet. 

With respect to the effect which might be produced upon our atmosphere by such a 
circumstance, it is impossible to offer anything but the most vague conjecture. Sir John 
Herschel was able to distinguish stars as minute as the 16th or 17th magnitude through 
the body of the comet ! Hence it seems reasonable to infer, that the nebulous matter of 
which it is composed, must be infinitely more attenuated than our atmosphere ; so that 
for every particle of cometary matter which we should inhale, we should inspire millions 
of particles of atmospheric air. 

543 This is one of the comets that was to come into collision 
with the Earth, and to blot it out from the Solar System. In 
returning to its perihelion, November 26th, 1832, it was comput- 
ed that it would cross the Earth's orbit at a distance of only 
18,500 miles. It is evident that if the Earth had been in that 
part of her orbit at the same time with the comet, our atmos- 
phere would have mingled with the atmosphere of the comet, 
and the two bodies, perhaps, have come in contact. But the 
comet passed the Earth's orbit on the 29th of October, in the 
8th degree of Sagittarius, and the Earth did not arrive at that 
point until the 30th of November, which was 32 days after- 
wards. 

If we multiply the number of hours in 32 days, by 63,000 (the velocity of the Earth pei 
hour), we shall find that the Earth was more than 52,000,000 miles behind the comet when 
it crossed her orbit. Its nearest approach to the Earth at any time, was about 51,000,000 
of miles ; its nearest approach to the Sun, was about 83,000,000 of miles. Its mean dis- 
tance from the Sun, or half the longest axis of its orbit, is 337,000,000 of miles. Its: 
eccentricity is 253,000,000 of miles ; consequently, it is 507,000,000 of miles nearer the 
Sun in its perihelion than it is in its aphelion. The period of its sidereal revolution is 
2460 days, or about 6% days. 

544. Although the comets of Encke and Biela arc objects of 
very great interest, yet their short periods, the limited space 
within which their motion is circumscribed, and consequently the 
very slight disturbance which they sustain from the attraction 
of the planets, render them of less interest to physical astrono- 
my than those of longer periods. They do not, like them, rush 
from the invisible and inaccessible depths of space, and, after 
sweeping our system, depart to distances with the conception of 
which the imagination itself is confounded. They possess none 
of that grandeur which is connected with whatever appears to 
break through the fixed order of the universe. 

What curious fact stated? What result if the Earth were to be enveloped in the comet? 
543. What mischief formerly anticipated from Biela's comet? Its return in 1S32 ? How 
near a collision in distance and in time ? Its nearest approach to the Earth? To the 
Sun ? Its mean distance from him ? Its eccentricity and period ? 544. Why are the 
cruets of short periods less interesting than others ? For what comet is it reserved 'o 
afford grounds fov the proudest triumphs of mathematical science? 



258 ASTRONOMY. 

It is reserved for the comet of Halley alone to afford the proudest triumphs to those 
powers of calculation by which we are enabled to follow it in the depths of space, 
2,000,000,000 of miles beyond the extreme verge of the solar system; and, notwithstand- 
ing the disturbances which render each succeeding period of its return different from 
the last, to foretell that return with precision. To be able to predict the very day and 
circumstances of the return of such a bodiless and eccentric wanderer, after the lapse 
of so many years, evinces a perfection of the astronomical calculus that may justly 
challenge our admiration. 

545. u The re-appearance of Biela's comet," says Herschel, 
" whose return in 1832 was made the subject of elaborate cal- 
culations by mathematicians of the first eminence, did not disap- 
point the expectations of astronomers. It is hardly possible to 
imagine anything more striking than the appearance, after the 
lapse of nearly seven years, of such an all but imperceptible 
cloud or wisp of vapor, true, however, to its predicted sime and 
place, and obeying laws like those which regulate the planets." 

Herschel, whose Observatory was at Slough, England, observed the daily progress of 
this comet from the 24th of September, until its disappearance, compared its actual posi- 
tion from day to day, with its calculated position, and found them to agree within four 
or five minutes of time in right ascension, and within & few seconds of declination. 
Its position, then, as represented on a planisphere which the author prepared for his 
pupils, and afterwards published, was true to within a less space than one-third of its 
projected diameter. Like some others that have been observed, this comet has no lumi- 
nous train by which it can be easily recognized by the naked eye, except when it is very 
near the Sun. This is the reason why it was not more generally observed at its late 
return. 

Although this comet is usually denominated "Biela's comet," yet it seems that 
M. Gambart, director of the Observatory at Marseilles, is equally entitled to the honor of 
identifying it with the comet of 1772, and of 1805. He discovered it only 10 days after 
Biela, and immediately set about calculating its elements from his own observations, which 
are thought to equal, if they do not surpass, in point of accuracy, those of every other 
astronomer. 

546. Up to the beginning of the 11th century, no correct 
notious had been entertained in respect to the paths of comets. 
Kepler's first conjecture was that they moved in straight lines ; 
but as that did not agree with observation, he next concluded 
that they were parabolic curves, having the Sun near the vertex, 
and running indefinitely into the regions of space at both extre- 
mities. There was nothing in the observations of the earlier 
astronomers to fix their identity, or to lead him to suspect that 
any one of them had ever been seen before ; much less that they 
formed a part of the solar system, revolving about the Sun in 
elliptical orbits that returned into themselves. 

541. This grand discovery was reserved for one of the most 
industrious and sagacious astronomers that ever lived — this was 
Dr. Halley, the cotemporary and friend of Newton. When the 
comet of 1682 made its appearance, he set himself about observ- 
ing it with great care, and found there was a wonderful resem- 

545. Remarks on the re-appearance of Biela's comet? What remarkable calculation 
referred to? Form of this comet? Is it really Biela's comet? 546. Former know- 
ledge of the orbits of comets? 547. What grand discovery, and by whom? Process 



COMETS THEIR NATURE, MOTIONS, ORBITS, ETC. 259 

blance between it and three other comets that he found recorded, 
the comets of 1456, of 1531, and 1607. The times of their 
appearance had been nearly at equal and regular intervals ; their 
perihelion distances were nearly the same ; and he finally proved 
them to be one and the same comet, performing its circuit around 
the Sun in a period varying a little from 76 years. It is, there- 
fore, called Halley's comet. (Map IX., Fig. 18.) 

The orbit of Halley's comet extends outward about 120,000,000 
of miles beyond the orbit of Neptune, as represented in the fol- 
lowing cut : 

ORBIT OF HALLET'S COMET. 



This is the same comet that filled the eastern world with so much consternation in 1456, 
as stated on page 253, and became an object of such abhorrence to the Church of Rome. 

The periodic times of the three comets just described, are as 
follow : 

Encke's, 1212 days. 
Biela's, 2461 days. 
Halley's, 28,000 days. 

Halley's comet, true to its predicted time and place, is now (Oct. 1S35) visible' in the 
evening sky. But we behold none of those phenomena which threw our ancestors of the 
middle ages into agonies of superstitious terror. We see not the cometa horrendai 
inagnitudinis, as it appeared in 1305, nor that tail of enormous length which, in 1456, 
extended over two-thirds of the interval between the horizon and the zenith, nor even a 
star as brilliant as was the same comet in 1682, with its tail of 30°. 

Its mean distance from the Sun is 1,713,700,000 miles ; the eccentricity of its orbit is 
1,658,000,000 miles ; consequently it is 3,316,000,000 miles farther from the Sun in its 
aphelion than it is in its perihelion. In the latter case its distance from the sun is only 
55,700,000 miles; but in the former it is 3,371,700,000 miles. Therefore, though its aphe- 
lion distance be great, its mean distance is less than that of Uranus ; and great as is the 
aphelion distance, it is but a very small fraction less than one-Jive thousandth part of 
that distance from the Sun, beyond which the very nearest of the fixed stars must.be 
situated; and, as the determination of their distance is negative and not positive, the 
nearest of them may be at twice or ten times that distance. 

of the discovery? Aphelion distance of Halley's comet? What former visit to our sys- 
tem referred to ? Periods of the three comets just described ? Appearance of Halley's 
comet in 1835? Its mean distance from the Sun? How compare with that of Uranui. ? 
How does his greatest distance compare with that of the Fixed Stars ? 



260 ASTRONOMY. 

548. The orbit of Encke's 0BBrrs 0F several oombts. 

comet is wholly within the orbit ^.- — -&_. 

of Jupiter, while that of Biela's ^ «*'" *"\ 

extends but a short distance /' \*> 

beyond it. The aphelion dis- / ^-&?^ 

tance of Halley's comet is __ .■" .^alley's isy Rs ,.- 

3,400,000,000 of miles, or I '.:;£* 

550,000,000 of miles beyond [ AO ;) 

the orbit of Neptune. And \ iV.';.;-./-- 

even this is, in reality, a comet \ \ / 

of short period compared with \ >;'' 

many that belong to our svs- \ ^fjf \^ 

tern. \---''J '\K. y 



549. The comet of 1819 wasre- , /" "^ :: - ---^....^^ 

markable for its straight wedge- •'''' 

shaped appearance — not altogether unlike a shuttle-cock. It 
exhibited none of that curvature in its form which is an almost 
universal characteristic of cometary bodies. Map IX., Fig. 79. 

550. The comet of 1843 was one of the most magnificent of 
modern times (See Map IX., Fig. 80). It was more than 60° 
in length. In the Southern Hemisphere it was so brilliant as 
to throw a very strong light upon the Earth. As its distance 
from the Sun varied, its color varied, from pale orange to "rose 
red," and then to white. "It passed its perihelion on the 27th 
of February, at which time it almost grazed the surface of the 
Sun, approaching nearer to that luminary than any comet 
hitherto observed. Its motions at this time were astonishingly 
swift, and its brilliancy such as to induce the belief that it was at 
a white heat through its whole extent. Its period is supposed 
to be 21-J years ; consequently this must be its eighth return 
since 1668 ; and it will visit our sphere again in 1865." 

At the time of the appearance of this comet, Rev. Mr. Miller and others were earnestly 
warning the people of the United States, that the world was to be burned up on the 23d 
of April following ; and the appearance of the comet was regarded by many as an indica- 
tion that the end of all things was at hand. 

551. The number of comets which have been observed since 
the Christian era, amounts to 700. Scarcely a year has passed 
without the observation of one or two. And since multitudes 
of them must escape observation, by reason of their traversing 
that part of the heavens which is above the horizon in the day 

54S. Where are the orbits of Encke's and Biela's comets situated? What said of Hal- 
ley's comet? 549. Comet of 1819? 550. That of 1843? Its length? Brilliancy? 
What variation in its color ? Its perihelion passage 1 Heat ? Its period ? Next appear- 
ance? Incident of its last appearance ? 551. Number of comets ? Why so few seen ? 



COMETS THEIR NATURE, MOTIONS, ORBITS, ETC. 261 

time, their whole number is probably many thousands. Comets 
so circumstanced, can only become visible by the rare coinci- 
dence of a total eclipse of the Sun — a coincidence which hap- 
pened, as related by Seneca, 60 years before Christ, when a 
large comet was actually observed very near the Sun. 

But M. Arago reasons in the following manner, with respect to the number of comets : — 
The number of ascertained comets, which, at their least distances, pass within the orbit 
of Mercury, is thirty. Assuming that the comets are uniformly distributed throughout 
the solar system, there will be 117,649 times as many comets included within the orbit of 
Uranus, as there are within the orbit of Mercury. But as there are 30 within the orbit 
of Mercury, there must be 3,529,470 within the orbit of Uranus ! 

552. Of 9T comets whose elements have been calculated by 
astronomers, 24 passed between the Sun and the orbit of Mer- 
cury: 33 between the orbits of Mercury and Yenus ; 21 between 
the orbits of Yenus and the Earth ; 15 between the orbits of 
Ceres and Jupiter. 49 of these comets move from easl^to west, 
and 49 in the opposite direction. The total number of distinct 
comets, whose paths during the visible part of their course had 
been ascertained, up to the year 1855, was about one hundred 
and fifty. 

553. What regions these bodies visit, when they pass beyond 
the limits of our view ; upon what errands they come, when 
they again revisit the central parts of our system ; what is the 
difference between their physical constitution and that of the 
Sun and planets ; and what important ends they are destined 
to accomplish in the economy of the Universe, are inquiries 
which naturally arise in the mind, but which surpass the limited 
powers of the human understanding at present to determine. 

554. Such is the celestial system with which our Earth was 
associated at its creation, distinct from the rest of the starry 
hosts. Whatever may be the comparative antiquity of our 
globe, and the myriads of radiant bodies which nightly gem the 
immense vault above us, it is most reasonable to conclude, that 
the Sun, Earth, and planets differ little in the date of their 
origin. This, fact, at least, seems to be philosophically certain, 
that all the bodies which compose our solar system must have 
been placed at one and the same time in that arrangement, and 
in those positions in which we now behold them ; because all 
maintain their present stations, and motions, and distances, by 
their mutual action on each other. Neither could it be where it 

Phenomenon 60 years before Christ? M. Arago's reasoning and conclusion? 552. 
Perihelion distances of various comets ? Directions in longitude ? Number whose paths 
have been ascertained? 553. What inquiries awakened by the visits of cometary 
bodies? 554. Remarks respecting the date of the solar system? What supposed proof 
that the whole system was created at once? 



262 ASTRONOMY. 

is, nor move as it does, nor appear as we see it, unless they 
were all co-existent. The presence of each is essential to the 
system — the Sun to them, they to the Sun, and all to each 
other. This fact is a strong indication that their formation was 
simultaneous. 



CHAPTER X. 

OF ffcE FORCES BY WHICH THE PLANETS ARE 
RETAINED m THEIR ORBITS. 

555. Having described the real and apparent motions of the 
bodies which compose the solar system, it may be interesting 
next to show, that these motions, however varied or complex 
they may seem, all result from one simple principle, or law, 
namely, the 

LAW OF UNIVERSAL GRAVITATION. 

By gravitation is meant, that universal law of attraction, by 
which every particle of matter in the system has a tendency to 
every other particle. This attraction, or tendency of bodies 
towards each other, is in proportion to the quantity of matter 
they contain. The Earth, being immensely large in comparison 
with all other substances in its vicinity, destroys the effect of 
this attraction between smaller bodies, by bringing them all to 
itself. 

It is said, that Sir Isaac Newton, when he was drawing to a close the demonstration of 
the great truth, that gravity is the cause which keeps the heavenly bodies in their orbits, 
was so much agitated with the magnitude and importance of the discovery he was about 
to make, that he was unable to proceed, and desired a friend to finish what the intensity 
of his feelings did not allow him to do. 

556. The attraction of gravitation is reciprocal. All bodies 
not only attract other bodies, but are themselves attracted, and 
both according to their respective quantities of matter. The 
Sun, the largest body in our system, attracts the Earth and all 
the other planets, while they in turn attract the Sun. The 

555. Subject of this chapter? What is meant by gravitation ? Upon what does the 
amount of this attraction depend? Influence of the Earth? Anecdote of Newton? 
556. Is attraction reciprocal? What illustration cited? Ways in which attraction 



LAW OF GRAVITATION. 263 

Earth, also, attracts the Moon, and she in turn attracts the 
Earth. A ball, thrown upwards from the Earth, is brought 
again to its surface ; the Earth's attraction not only counter- 
balancing that of the ball, but also producing a motion of the 
ball towards itself. 

This disposition, or tendency towards the Earth, is manifested in whatever falls, whether 
it be a pebble from the hand, an apple from a tree, or an avalanche from a mountain. 
All terrestial bodies, not excepting the waters of the ocean, gravitate towards the center 
of the Earth, and it is by the same power that animals on all parts of the globe stand 
with their feet pointing to its center. 

55*1. The power of terrestial gravitation is greatest at the 
Earth's surface, whence it decreases both upwards and down- 
wards ; but not both ways in the same proportion. It decreases 
upwards as the square of the distance from the Earth's center 
increases ; so that at a distance from the center equal to twice 
the semi-diameter of the Earth, the gravitating force would be 
only one-fourth of what it is at the surface. But below the sur- 
face, it decreases in the direct ratio of the distance from the 
center ; so that at a distance of half a semi-diameter from the 
center, the gravitating force is but half of what it is at the 
surface. 

Weight and Gravity, in this case, are synonymous terms. We say a piece of lead 
weighs a pound, or 16 ounces ; but if by any means it could be raised 4000 miles above 
the surface of the Earth, which is about the distance of the surface from the center, and 
consequently equal to two semi-diameters of the Earth above its center, it would weigh 
only one-fourth of a pound, or four ounces ; and if the same weight could be raised to an 
elevation of 12,000 miles above the surface, or four semi-diameters above the center of 
the Earth, it would there weigh only one-sixteenth of a pound, or one ounce. 

558. The same body, at the center of the Earth, being equally 
attracted in every direction, would be without weight ; at 1000 
miles from the center it would weigh one-fourth of a pound : at 
2000 miles, one-half of a pound ; at 3000 miles, three-fourths of 
a pound ; and at 4000 miles, or at the surface, one pound. 

It is a universal law of attraction, that its power decreases as 
the square of the distance increases. The converse of this is also 
true, viz.: The power increases as the square of the distance 
decreases. Giving to this law the form of a practical rule, it will 
stand thus : 

The gravity of bodies above the surface of the Earth decreases 
in a duplicate ratio (or as the squares of their distances), in semi- 
diameters of the Earth, from the Earth's center. That is, when 

manifests itself ? 557. Where is the power of terrestrial gravitation greatest? How 
diminished ? In what ratio as we ascend above the Earth ? As we descend toward its 
center? Are weight and gravity the same ? 558. What would be the weight of a body 
at the Earth's center ? At 100 miles from the center ? At 2000 miles ? At 4000 ? What 
universal law? What rule based upon this law? What illustrations given? What rule 



264 ASTRONOMY. 

the gravity is increasing, multiply the weight by the square of 
the distance ; but when the gravity is decreasing, divide the 
weight by the square of the distance. 

Suppose a body weighs 40 pounds at 2000 miles above the Earth's surface, what would 
it weigh at the surface, estimating the Earth's semi-diameter at 4000 miles. From the 
center to the given height, is ljg semi-diameters ; the square of 1%, or 1.5 is 2.25, which, 
multiplied into the weight (40), gives 90 pounds, the answer. 

Suppose a body which weighs 256 pounds upon the surface of the Earth, be raised to 
the distance of the Moon (240,000 miles), what would be its weight? Thus, 4000)240,000(60 
semi-diameters, the square of which is 3600. As the gravity in this case is decreasing, 
divide the weight by the square of the distance, and it will give 3600)256(l-16th of a 
pound, or 1 ounce. 

To find to what height a given weight must be raised to lose a certain portion of its 
weight. 

Rule. — Divide the weight at the surface oy the required weight, and extract the 
square root of the quotient. Ex. A boy weighs 100 pounds, how high must he be carried 
to weigh but 4 pounds ? Thus, 100 divided by 4, gives 25, the square root of which is 5 
semi-diameters, or 20,000 miles above the center. 

559. Bodies of equal magnitude do not always contain equal 
quantities of matter ; a ball of cork, of equal bulk with one of 
lead, contains less matter, because it is more porous. The Sun, 
though fourteen hundred thousand times larger than the Earth, 
being much less dense, contains a quantity of matter only 
355,000 as great, and hence attracts the Earth with a force only 
355,000 times greater than that with which the Earth attracts 
the Sun. 

The quantity of matter in the Sun is 780 times greater than that of all the planets and 
satellites belonging to the Solar System ; consequently, their whole united force of attrac- 
tion is 780 times less upon the Sun, than that of the Sun upon them. 

CENTEB OF GRAVITY. 




560. The Center of Gravity of a body, is that point in which 
its whole weight is concentrated, and upon which it would rest, 
if freely suspended. If two weights, one of ten pounds, the 
other of one pound, be connected together by a rod eleven feet 
long, nicely poised on a center, and then be thrown into a free 
rotary motion, the heaviest will move in a circle with a radius of 
one foot, and the lightest will describe a circle with a radius of 
ten feet ; the center around which they move is their common 
center of gravity. (See the Figure.) 

to find what height a given weight must be raised to lose a certain portion of its 
weight? 559. Do bodies attract in proportion to their bulk? Why not? What illus- 
trations? Quantity of matter in the Sun? 560. What is meant by the center of 
gravity? niustration? How with the Sun and planets ? How would it be if there was 



ATTRACTIVE AND PROJECTILE FORCES. 265 

Thus the Sun and planets move around in an imaginary point 
as a center, always preserving an equilibrium. 

If there were but one body in the universe, provided it were of uniform density, the 
center of it would be the center of gravity towards which all the surrounding portions 
would uniformly tend, and they would thereby balance each other. Thus the center of 
gravity, and the body itself, would for ever remain at rest. It would neither move up nor 
down ; there being no other body to draw it in any direction. In this case, the terms up 
and down would have no meaning, except as applied to the body itself, to express the 
direction of the surface from the center. 

561. Were the Earth the only body revolving about the Sun, 
as the Sun's quantity of matter is 355,000 times as great as 
that of the Earth, the Sun would revolve in a circle equal only 
to the three hundred and fifty-five thousandth part of the Earth's 
distance from it ; but as the planets in their several orbits vary 
their positions, the center of gravity is not always at the same 
distance from the Sun. 

The quantity of matter in the Sun so far exceeds that of all 
the planets together, that were they all on one side of him, he 
would never be more than his own diameter from the common 
center of gravity ; the Sun is, therefore, justly considered as the 
center of the system. 

562. The quantity of matter in the Earth being about 80 
times as great as that of the Moon, their common center of 
gravity is 80 times nearer the former than the latter, which is 
about 3000 miles from the Earth's center. The secondary planets 
are governed by the same laws as their primaries, and both 
together move around a common center of gravity. Every sys- 
tem in the universe is supposed to revolve in like manner, around 
one common center. 

ATTRACTIVE AND PROJECTILE FORCES. 

563. All simple motion is naturally rectilinear ; that is, all 
bodies put in motion would continue to go forward in straight 
lines, as long as they met with no resistance or diverting force. 
On the other hand, the Sun, from his immense size, would, by 
the power of attraction, draw all the planets to him, if his 
attractive force were not counterbalanced by the primitive im- 
pulse of the planetary bodies to move in straight lines. 

564. The attractive power of a body drawing another body 

but one body in the universe? 561. Suppose the Earth was the only body revolving 
around the Sun ? Is the center of gravity always at the same distance from the Sun ? 
Why not ? How would it be if all the planets were on one side of him ? 562. What is 
the amount of matter in the Earth as compared with the Moon? How with the second- 
ary planets? With other systems in the universe? 563. What is the character of all 
simple motion? What illustrations given ? 564 What is the attractive power called ? 



266 ASTRONOMY. 

towards the center, is denominated Centripetal force ; and the ten- 
dency of a revolving body to fly from the center in a tangent 
line, is called the Projectile or Centrifugal force. The joint 
action of these two central forces gives the planets a circular 
motion, and retains them in their orbits as they revolve, the pri- 
maries about the Sun, and the secondaries about their primaries. 

565. The degree of the Sun's attractive power at each par- 
ticular planet, whatever be its distance, is uniformly equal to 
the centrifugal force of the planet. The nearer any planet is to 
the Sun, the more strongly is it attracted by him ; the farther 
any planet is from the Sun, the less is it attracted by him ; 
therefore, those planets which are the nearer to the Sun, must 
move the faster in their orbits, in order thereby to acquire cen- 
trifugal forces equal to the power of the Sun's attraction ; and 
those which are the farther from the Sun, must move the slower, 
in order that they may not have too great a degree of centri- 
fugal force, for the weaker attraction of the Sun at those 
distances. 

LAWS OF PLANETARY MOTION. 

566. Three very important laws, governing the movements of 
the planets, were discovered by Kepler, a German astronomer, 
in 1609. In honor of their discoverer, they are called Kepler's 
Laws. Kepler was a disciple of Tycho Brake, a noted astrono- 
mer of Denmark, and was equally celebrated 

with his renowned tutor. His residence and , ..--* -^ 
observatory were at Wirtemburgh, in Ger- /'' \ 

many. / \ 

The first of these laws is, that the orbits of i \ 

all the planets are elliptical, having the Sun in • 
the common focus. \ S"$k 

Thp nnint. in n nlnnpf's nrhit. npnrpsf t.hp Sun ia pnllprl fhp \ %MA\W 



The point in a planet's orbit nearest the Sun is called the 
perihelion point, and the point most remote the aphelion point. 
Perihelion is from peri, about or near, and helios, the Sun ; and 
aphelion, from apo, from, and helios, the Sun. 



«« 

W 



PERIHELION. 



Prom this first law of Kepler, it results that the planet3 move with different velocities, 
in different parts of their orbits. Prom the- aphelion to the perihelion points, the 
centripetal force combines with the centrifugal to accelerate the planet's motion ; 
while from perihelion to aphelion points, the centripetal acts against the centrifugal 
force, and retards it. 

The tendency to depart from the center? What does the joint action of these two forces 
produce ? 565. What relation between the Sun's attraction and the centrifugal force 
of the planets? What effect has the distance of a planet from the Sun, upon his attrac- 
tive force ? How is this increased tendency counterbalanced ? 566. What important 
laws — when and by whom discovered? State the first? What are the aphelion and 
perihelion points ? Derivation ? What results from this first law ? 



LAWS OF PLANETARY MOllON. 



267 



\ 



;/ 



/ 



RADIUS VECTOR. 
-©• 



From A to B in the diagram, the centrifugal force, 
represented by the line C, acts with the tendency to 
revolve, and the planet's motion is accelerated; but 
from B to A the same force, shown by the line D, acts 
against the tendency to advance, and the planet is .■ 

retarded. Hence it comes to aphelion with its least / 
velocity, and to perihelion with its greatest. ^ 

In the statement of velocities on page 45, the. mean ■ \ 
or average velocity is given. • 

561. The second law is, that the radius \ f 
vector of a planet describes equal areas in \ \ 
equal times. The radius is an imaginary \ 
line joining the center of the Sun and V 
the center of the planet, in any part of 
its orbit. Vector is from veho, to carry ; 

hence the radius vector is a radius carried ! — "*" 

round. By the statement that it describes equal areas in equal 
times, is meant that it sweeps over the same surface in an hour, 
when a planet is near the Sun, and moves swiftly, as, when 
furthest from the Sun, it moves most slowly. 

The nearer a planet is to the Sun, the more rapid its 
motion. It follows, therefore, that if the orbit of a 
planet is an ellipse, with the Sun in one of the foci, its 
rate of motion will be unequal in different parts of its 
orbit — swiftest at perihelion, and slowest at aphelion. 
From perihelion to aphelion the centripetal more di- 
rectly counteracts the centrifugal force, and the planet 
is retarded. On the other hand, from the aphelion to 
the perihelion point, the centripetal and centrifugal 
forces are united, or act in a similar direction. They 
consequently hasten the planet onward, and its rate of 
motion is constantly accelerated. Now suppose, when 
the planet is at a certain point near its perihelion, we 
draw a line from its center to the center of the Sun. 
This line is the radius vector. At the end of one day, 
for instance, after the planet has advanced considera- 
bly in its orbit, we draw another line in the same man- 
ner to the Sun's center, and estimate the area between 
the two lines. At another time, when the planet is near 
its aphelion, we note the space over which the radius vector travels in one day, and esti- 
mate its area. On comparison, it will be found, that notwithstanding the unequal 
velocity of the planet, and consequently of the radius vector, at the two ends of the 
ellipse, the area over which the radius vector has traveled is the same in both cases. 
The same principle obtains in every part of the planetary orbits, whatever may be their 
ellipticity or the mean distance of the planet from the Sun ; hence the rule that the 
radius vector describes equal areas in equal times. In the preceding cut, the twelve 
triangles, numbered 1, 2, 3, &c, over each of which the radius vector sweeps in equal 
times, are equal. 

568. The third law of Kepler is, that the squares of the periodic 
times of any two planets are proportioned to the cubes of their mean 
distances from the Sun. 

Take, for example, the Earth and Mars, whose periods are 365-2564 and 686-9796 days, 
and whose distances from the Sun are in the proportion of 1 to 1-52369, and it will be 
found that (365.2564)2 : (686.9796)2 : : (1)3 : (1.52369)3. 




567. State the 
illustration ? 



law of Kepler? Explain it? 

B-G. 12 



568. The third law? What 



268 ASTRONOMY. 

According to these laws, which are known to prevail throughout the solar system, 
many of the facts of astronomy are deduced from other facts previously ascertained. 
They are, therefore, of great importance, and should be studied till they are, at least, 
thoroughly understood, if not committed to memory. 

569. From the foregoing principles, it follows, that the force 
of gravity, and the centrifugal force, are mutual opposing powers 
— each continually acting against the other. Thus, the weight 
of bodies on the Earth's equator, is diminished by the centrifugal 
force of her diurnal rotation, in the proportion of one pound for 
every 290 pounds : that is, had the Earth no motion on her 
axis, all bodies on the equator would weigh one two hundred and 
eighty-ninth part more than they now do. 

On the contrary, if her diurnal motion were accelerated, the centrifugal force would be 
proportionally increased, and the weight of bodies at the equator would be in the same 
ratio diminished. Should the Earth revolve upon its axis with a velocity which would 
make the day but 84 minutes long, instead of 24 hours, the centrifugal force would coun- 
terbalance that of gravity, and all bodies at the equator would then be absolutely desti- 
tute of weight; and if the centrifugal force were further augmented (the Earth revolving 
in less than 84 minutes), gravitation would be completely overpowered, and all fluids 
and loose substances near the equator would fly off from the surface. 

570. The weight of bodies, either upon the Earth, or on any 
other planet having a motion around its axis, depends jointly 
upon the mass of the planet, and its diurnal velocity. A body 
weighing one pound upon the equator of the Earth, would 
weigh, if removed to the equator of the Sun, 27.9 lbs.; of Mer- 
cury, A. 03 lbs. ; of Yenus, 0.98 lbs.; of the Moon, l-6th of a-lb. ; 
of Mars, \ lb. ; of Jupiter, 2.716 lbs. ; of Saturn, 1.01 lbs. 



CHAPTER XI. 

PEOPER MOTION OF THE SUN IN SPACE. 

571. Though we are accustomed to speak of the Sun as the 
■fixed center of the Solar System, the idea of his fixedness is cor- 
rect only so far as his relation to the bodies revolving around 
him are concerned. As the planets accompanied by their satel- 
lites revolve around the Sun, so he is found to be moving with 
all his retinue of worlds, in a vast orbit, around some distant and 
unknown center. 

569. What results from these principles, as respects the weight of bodies on the Earth's 
surface? How increased or diminished? What illustrations given? 570. Upon 
what, then, does the weight of bodies upon the planets depend ? What illustrations ? 
6T1. Is the Sun a fixed body? What motion in space? Who first advanced this idea? 



PROPER MOTION OF THE SUN IN SPACE. 269 

This opinion was first advanced, we think, by Sir William Herschel ; but the honor of 
actually determining this interesting fact, belongs to Struve, who ascertained not only 
the direction of the Sun and Solar System, but also their velocity. The point of tend- 
ency is towards the constellation Hercules, Right Ascension 259°, Declination 35°. The 
velocity of the Sun, &c, in space, is estimated at about 20,000 miles per hour, or nearly 
8 miles per second ; 

572. With this wonderful fact in view, we may no longer con- 
sider the Sun as fixed and stationary, but rather as a vast and 
luminous planet, sustaining the same relation to some central 
orb, that the primary planets sustain to him, or that the second- 
aries sustain to their primaries. Nor is it necessary that the 
stupendous mechanism of nature should be restricted even to 
these sublime proportions. The Sun's central body may also 
have its orbit, and its center of attraction and motion, and so on, 
till, as Dr. Dick observes, we come to the great center of all— to 
the Throne of God. 

THE CENTRAL SUN. 

573. In 1847, an article appeared in several European jour- 
nals, announcing the probable discovery by Professor Madler, 
of Dorpat, of the Sun's central orb ; the inclination of his orbit 
to the plane of the ecliptic ; and his periodic time I 

By an extensive and laborious comparison of the quantities 
and directions of the proper motions of the stars in various parts 
of the heavens, combined with indications afforded by the paral- 
laxes hitherto determined, and with the theory of universal gra- 
vitation, Professor Madler arrived at the conclusion that the 
Pleiades form the central group of our whole astral or sidereal 
system, including the Milky Way and all the brighter stars, but 
exclusive of the more distant nebulae, and of the stars of which 
those nebulae may be composed. And within this central group 
itself he has been led to fix on the star Alcyone, as occupying 
exactly or nearly the position of the center of gravity, and as 
entitled to be called the central Sun. 

Assuming BessePs parallax of the star 61 Cygni, long since remarkable for its larger 
proper motion, to be correctly determined, Madler proceeds to form a first approximate 
estimate of the distance of this central body from the planetary or solar system ; and 
arrives at the provisional conclusion, that Alcyone is about 34,000,000 times as far removed 
from us, or from our own Sun, as the latter luminary is from us. It would, therefore, 
according to this estimation, be at least a million times as distant as the new planet, of 
which the theoretical or deductive discovery has been so great and beautiful a triumph 
of modern astronomy, and so striking a confirmation of the law of Newton. The same 
approximate determination of distance conducts to the result, that the light of the cen- 
tral sun occupies more than five centuries in travelling thence to us. 

Direction and velocity of the Sun and Solar System ? 572. How, then, should we 
regard the Sun? What further speculation? Dr. Dick's observation? 573. What 
great discovery in 1847, and by whom? By what process? What conclusion first 
reached ? What star afterward designated ? Further description of the progress of the 
discovery ? What conclusion respecting the passage of light from the central Sun to us ? 



270 



ASTRONOMY. 



r h i mi 1 • i. ARC OF THE SON'S ORBIT 

574. The enormous orbit 
which our own Sun, with the 
Earth, and the other planets, 
is thus inferred to be describ- 
ing about that distant cen- 
ter — not, indeed, under its 
influence alone, but by the 
combined attractions of all 
the stars which are nearer to 
it than we are, and which are 
estimated to amount to more 
than 111,000,000 of masses, 
each equal to the total mass 
of our own Solar System — 
is supposed to require upwards 
of eighteen millions of years for 
its complete description, at the rate of about eight geographical 
miles in every second of time. At this rate, the arc of its orbit, 
over which the Sun has traveled since the creation of the world, 
amounts to only about 3- oVo- tn P ar ^ °f hi s orbit, or about t 
minutes — an arc so small, compared with the whole, as to be 
hardly distinguishable from a straight line. 

The plane of this vast orbit of the Sun is judged to have an inclination of about 84 
degrees to the ecliptic, or to the plane of the annual orbit of the Earth ; and the longitude 
of the ascending node of the former orbit on the latter is concluded to be nearly 232 
degrees. 




CHAPTER XII. 



PRECESSION OF THE EQUINOXES— OBLIQUITY OF THE 
ECLIPTIC. 

5T5. Of all the motions which are going forward in the Solar 
System, there is none, which it is important to notice, more 
difficult to comprehend, or to explain, than what is called the 

PRECESSION OF THE EQUINOXES. 

The equinoxes, as we have learned, are the two opposite 

574. Supposed period of the Sun's revolution ? What portion of his orbit gone over 
eince the creation of our race ? Situation of his orbit with respect to the ecliptic? Lon- 
gitude of ascending node? 575. Subject of this chapter? What are the equinoxes ? 



PRECESSION OF THE EQUINOXES. 



271 



points in the Earth's orbit, where it crosses the celestial equator. 
The first is in Aries ; the other, in Libra. By the precession of the 
equinoxes is meant, that the intersection of the equator with the 
ecliptic is not always in the same point : — in other words, that 
the Sun, in its apparent annual course, does not cross the equi- 
noctial, Spring and Autumn, exactly in the same points, but 
every year a little behind those of the preceding year. 

576. This annual falling back of the equinoctial points, is 
called by astronomers, with reference to the motion of the 
heavens, the Precession of the Equinoxes; but it would better 
accord with fact as well as the apprehension of the learner, to 
call it, as it is, the Recession of the Equinoxes ; for the equinoc- 
tial points do actually recede upon the ecliptic, at the rate of 
about 50^" of a degree every year. It is the name only, and 
not the position, of the equinoxes which remains permanent. 
Wherever the Sun crosses the equinoctial in the spring, there is 
the vernal equinox ; and wherever he crosses it in the autumn, 
there is the autumnal equinox ; and these points are constantly 



PRECESSIOX OF THS EQUINOXES. 



moving to the west. 

To render this sublet familiar, 
we will suppose two carriage roads, 
extending quite around the Earth ; 
one, representing the equator, run- 
ning due east and west; and the 
other representing the ecliptic, run- 
ning nearly in the same direction as 
the former, yet so as to cross it with 
a small angle (say of 23%°), both at 
the point where we now stand, for 
instance, and in the nadir, exactly 
opposite ; let there also be another 
road, to represent the prime meri- 
dian, running north and south, and 
crossing the first at right angles, in 
the common point of intersection, as 
in the annexed figure. 

Let a carriage now start from this 
point of intersection, not in the road 
leading directly east, but along that 
of the ecliptic, which leaves the 
former a little to the north, and let 
a person be placed to watch when 
the carriage comes around again, 
after having made the circuit of the 
Earth, and see whether the carriage 
will cross the equinoctial road again 

precisely in the same track as when it left the goal. Though the person stood exactly 
in the former track, he need not fear being run over, for the carriage will cross the 
road 100 rods west of him, that is 100 rods west of the meridian on which he stood. It is 
to be observed, that 100 rods on the equator is equal to 50 % seconds of a degree. 

If the carriage still continue to go around the Earth, it will, on completing its second 




What meant by their precession ? 576. With reference to what is it a precession? Is 
it really a precession of the equinoxes ? Where are the equinoxes spring and fall ? Can 
you illustrate by the two carriage roads, &c. ? By the other diagram? Does the Sun 



272 



ASTRONOMY. 




circuit, cross the equinoctial path 200 rods west of the meridian whence it first set out ; 
on the third circuit, 300 rods west ; on the fourth circuit, 400 rods, and so on, continually. 
After 71% circuits, the point of intersection would be one degree west of its place at the 
commencement of the route. At this rate it would be easy to determine how many com- 
plete circuits the carriage must perform before this continual falling back of the inter- 
secting point would have retreated over every degree of the orbit, until it reached again 
the point from whence it first departed. The application of this illustration will be mani- 
fest when we consider, further, 

that this interesting phenomenon recession of the equinoxes. 

may be explained in another 
way by the adjoining diagram. 
Let the point A represent the 
vernal equinox, reached, for in- 
stance, at 12 o'clock on the 20th 
of March. The next year the 
Sun will be in the equinoctial 22 
minutes 33 seconds earlier, at 
which time the Earth will be 
50%" on the ecliptic, back of the 
point at which the Sun was in 
the equinoctial the year before. 
The next year the same will oc- 
cur again ; and thus the equi- 
noctial point will recede west- 
ward little by little, as shown by 
the small lines from A to B, and 
from C to D. It is in reference 
to the stars going forward, or 
seeming to precede the equi- 
noxes, that the phenomenon is 
called the Precession of the Equi- 
noxes. But in reference to the 
motion of the equinoxes them- 
selves, it is rather a recession. 

577. The Sun revolves from one equinox to the same equinox 
again, in 365d. 5h. 48' 41 ".81. This constitutes the natural, or 
tropical year, because, in this period, one revolution of the sea- 
sons is exactly completed. But it is, meanwhile, to be borne in 
mind, that the equinox itself, during this period, has not kept 
its position among the stars, but has deserted its place, and 
fallen hack a little way to meet the Sun ; whereby the Sun has 
arrived at the equinox before he has arrived at the same position 
among the stars from which he departed the year before ; and, 
consequently, must perform as much more than barely a tropical 
revolution, to reach that point again. 

To pass over this interval, which completes the Sun's sidereal 
revolution, takes (20' 22". 94) about 22 minutes and 23 seconds 
longer. By adding 22 minutes and 23 seconds to the time of a 
tropical revolution, we obtain 365d. 6h. 9m. lOfs. for the length 
of a sidereal revolution ; or the time in which the Sun revolves 
from one fixed star to the same star again. 

Though we speak of the revolution of the Sun, we mean simply his apparent revolution 
eastward around the heavens, caused wholly by the actual revolution of the Earth in her 

actually revolve? Why, then, speak of his revolution? 577. What is the length of a 
tropical year ? How different from a sidereal year ? Difference of Hme t Length of a 
sidereal year ? 



PRECESSION OF THE EQUINOXES. 



273 



orbit, as a distant object would appeal- to sweep around the horizon if we were walking 
or sailing around it. This may be illustrated by the cut, page 288, where the passage 
of the Earth from A to B would cause the Sun to appear to move from C to D ; and so oa 
around the whole circle of the Zodiac. 

518. As the Sun describes the whole ecliptic, or 360°, in a 
tropical year, he moves over 59' 8£" of a degree every day, at a 
mean rate, which is equal to 50^" of a degree in 20 minutes and 
23 seconds of time ; consequently he will arrive at the same 
equinox or solstice when he is 50^" of a degree short of the same 
star or fixed point in the heavens, from which he set out the 
year before. So that, with respect to the fixed stars, the Sun 
and equinoctial points fall back, as it were, 1° in llf years. 
This will make the stars appear to have gone forward 1°, with 
respect to the signs in the ecliptic, in that time ; for it must be 
observed, that the same signs always keep in the same points of the 
ecliptic, without regard to the place of the constellations. Hence it 
becomes necessary to have new plates engraved for celestial 
globes and maps, at least once in 50 years, in order to exhibit 
truly the altered position of the stars. At the present rate of 
motion, the recession of the equinoxes, as it should be called, or 
the precession of the stars, amounts to 30°, or one whole sign, in 
2140 years. 

PRECESSION OF THE STABS. 




To explain this by a figure : Suppose the Sun to have been in conjunction with a fixed 
star at S, in the first degree of Taurus (the second sign of the ecliptic), 340 years before 
the birth of our Saviour, or about the seventeenth year of Alexander the Great ; then 
having made 2140 revolutions through the ecliptic, he would be found again at the end of 
so many sidereal years at S ; but at the end of so many Julian years, he would be found 
at J, and at the end of so many tropical years, which would bring it down to the begin- 
ning of the present century, he would be found at T, in the first degree of Aries, which 



578. Daily progress of the Sun ? What is the amount of the annual recession of the 
equinoxes? What effect will this have upon the apparent positions of the stars ? Hence 
what becomes necessary? How long does it require for the equinoxes to recede a whole 
sign? Do you understand the diagram, and the reference to the sidereal, Julian, and 
Tropical years? Explain the difference in these three kinds of years. 



274 ASTRONOMY. 

has receded from S to T in that time by the precession of the equinoctial points Aries and 
Libra. The arc S T would be equal to the amount of the precession {for precession we 
must still call it) of the equinox in 2140 years, at the rate of 50".23572 of a degree, or 20 
minutes and 23 seconds of time annually, as above stated. 

5V9. From the constant retrogradation of the equinoctial 
points, and with them of all the signs of the ecliptic, it follows 
that the longitude of the stars must continually increase. The same 
cause affects also their right ascension and declination. Hence, 
those stars which, in the infancy of astronomy, were in the sign 
Aries, we now find in Taurus ; and those which were in Taurus, 
we now find iu Gemini, and so on. Hence likewise it is, that 
the star which rose or set at any particular time of the year, in 
the time of Hesiod, Eudoxus, Virgil, Pliny, and others, by no 
means answers at this time to their descriptions. 

Hesiod, in his Opera et Dies, lib. ii. verse 185, says : 

" When from the solstice sixty wintry days 
Their turns have finished, mark, with glitt'ring rays, 
From Ocean's sacred flood, Arcturus rise, 
Then first to gild the dusky evening skies." 

But Arcturus now rises acronically in latitude 37° 45' N. the latitude of Hesiod, and 
nearly that of Richmond, in Virginia, about 100 days after the winter solstice. Suppos- 
ing Hesiod to be correct, there is a difference of 40 days arising from the precession of 
the equinoxes since the days of Hesiod. Now, as there is no record extant of the exact 
period of the world when this poet flourished, let us see to what result astronomy will 
lead us. 

As the Sun moves through about 39° of the ecliptic in 40 days, the winter solstice, in 
the time of Hesiod, was in the 9th degree of Aquarius. Now, estimating the precession 
of the equinoxes at 505^" in a year, we shall have 50i£" : 1 year : : 39 : 2814 years since the 
time of Hesiod : if we subtract from this our present era, 1S55, it will give 958 years before 
Christ. Lempriere, in his Classical Dictionary, says Hesiod lived 907 years before Christ. 
See a similar calculation for the time of Thales, page 39. 

580. The retrograde movement of the equinoxes, and the 
annual extent of it, were determined by comparing the longitude 
of the same stars, at different intervals of time. The most care- 
ful and unwearied attention was requisite in order to determine 
the cause and extent of this motion — a motion so very slow as 
scarcely to be perceived in an age, and occupying not less than 
25,000 years in a single revolution. It has not yet completed 
one quarter of its first circuit in the heavens since the creation 
of Mars. 

581. This observation has not only determined the absolute 
motion of the equinoctial points, but measured its limit ; it has 
also shown that this motion, like the causes which produce it, is 
not uniform in itself ; but that it is constantly accelerated by a 

579. What effect has the recession of the equinoxes upon the longitude of the stars, and 
their right ascension and declination ? Hence what results ? What interesting calcu- 
lation in reference to Hesiod? 580. How were this recession and its extent determined? 
What necessary? Time of complete revolution? Amount since creation? 581. Is 
this retrogression uniform? Amount of acceleration ? What illustration given ? 



PRECESSION OF THE EQUINOXES. 275 

slow arithmetical increase of 1" of a degree in 4100 years. A 
quantity which, though totally inappreciable for short periods of 
time, becomes sensible after a lapse of ages. 

For example : The retrogradation of the equinoctial points is now greater by nearly %' 
than it was in the time of Hipparchus, the first who observed this motion ; consequently, 
the mean tropical year is shorter now by about 12 seconds than it was then. For, since 
the retrogradation of the equinoxes is now every year greater than it was then, the Sun 
has, each year, a space of nearly % " less to pass through in the ecliptic, in order to reach 
the plane of the equator. Now the Sun is 12 seconds of time in passing over %* of space. 

582. At present, the equinoctial points move backwards, or 
from east to west along the path of the ecliptic at the rate of 1° 
in 7 If years, or one whole sign in 2140 years. Continuing at 
this rate, they will fall back through the whole of the 12 signs 
of the ecliptic in 25,680 years, and thus return to the same posi- 
tion among the stars, as in the beginning. 

But in determining the period of a complete revolution of the 
equinoctial points, it must be borne in mind that the motion itself 
is continually increasing ; so that the last quarter of the revolu- 
tion is accomplished several hundred years sooner than the first 
quarter. Making due allowance for this accelerated progress, 
the revolution of the equinoxes is completed in 25,000 years ; 
or, more exactly, in 24,992 years. 

Were the motion of the equinoctial points uniform ; that is, did they pass through 
equal portions of the ecliptic in equal times, they would accomplish their first quarter, or 
pass through the first three sig?is of the ecliptic, in 6250 years. But they are 6575 years 
in passing through the first quarter ; about 21S years less in passing through the second 
quarter ; 218 less in passing through the third, and so on. 

583. The immediate consequence of the precession of the equi- 
noxes, as we have already observed, is a continually progressive 
increase of longitude in all the heavenly bodies. For the vernal 
equinox being the initial point of longitude, as well as <* e right 
ascension, a retreat of this point on the ecliptic tells upon the 
longitude of all alike, whether at rest or in motion, and pro- 
duces, so far as its amount extends, the appearance of a motion 
in longitude common to them all, as if the whole heavens had a 
slow rotation around the poles of the ecliptic in the long period 
above mentioned, similar to what they have in every twenty-four 
hours around the poles of the equinoctial. As the Sun loses one 
day in the year on the stars, by his direct motion in longitude ; 
so the equinox gains one day on them in 25,000 years, by its 
retrograde motion. 

5S2. Present rate of motion ? Exact period at **.is rate ? Period making allowance 
for acceleration ? Time of passing over the first quarter of the ecliptic ? The second ? 
Third? 533. What immediate consequences of the precession of the equinoxes? 
Why does it affect the longitude of the stars ? What resemblance between the motion of 
the celestial sphere and that of the Earth ? Between the Sun and equinoxes ? 

12* 



276 



ASTRONOMY. 



584. The cause of this motion was unknown, until Newton 
proved that it was a necessary consequence of the rotation of 
the Earth, combined with its elliptical figure, and the unequal 
attraction of the Sun and Moon on its polar and equatorial 
regions. There being more matter about the Earth's equator 
than at the poles, the former is more strongly attracted than 
the latter, which causes a slight gyratory or wabbling motion of 
the poles of the Earth around those of the ecliptic, like the pin 
of a top about its center of motion, when . it spins a little 
obliquely to the base. 

585. The precession of the equinoxes, thus explained, consists 
in a real motion of the pole of the heavens among the stars, in a 
small circle around the pole of the ecliptic as a center, keeping 
constantly at its present distance of nearly 23£° from it, in a 
direction from east to west, and with a progress so very slow, 
as to require 25,000 years to complete the circle. During this 
revolution, it is evident that the pole will point successively to 
every part of the small circle in the heavens which it thus 
describes. Now this cannot happen without producing corre- 
sponding changes in the apparent diurnal motion of the sphere, 
and in the aspect which the heavens must present at remote 
periods of time. 



NUTATION OF THE EARTH'S AXIS. 
B 



Let the line A A in the figure re- 
present the plane of the ecliptic; 
B B, the poles of the ecliptic ; C C, 
the poles of the Earth ; and D D, the 
equinoctial. E E is the obliquity of 
the ecliptic. The star C, at the top, 
represents the pole star, and the 
curve line passing to the right from 
it, may represent the circular orbit 
of the north pole of the heavens 
around the north pole of the ecliptic. 

586. The effect of such 
a motion on the aspect of 
the heavens, is seen in the 
apparent approach of some 
stars and constellations to 
the celestial pole, and the 
recession of others. The 
bright star of the Lesser 

Bear, which we call the pole star, has not always been, nor will 
always continue to be, our polar star. At the time of the con- 

584. What said of the cause of this recession? 585. Of what, then, does it consist? 
What said of the pole of the ecliptic, and the aspects of the heavens during this revolu- 
tion? 585. How is the effect of this motion manifested? How with the Pole star? 




PKECESSION OF THE EQUINOXES. 277 

struction of the earliest catalogue, this star was 12° from the 
pole ; it is now only 1° 34' from it, and it will approach to 
within half a degree of it ; after which it will again recede, and 
slowly give place to others, which will succeed it in its proximity 
to the pole. 

The pole, as above considered, is to be understood, merely, as tbe 'vanishing point of 
the Earth's axis ; or that point in the concave sphere which is always opposite the 
terrestial pole, and which consequently must move as that moves. 

587. The precession of the stars in respect to the equinoxes, 
is less apparent the greater their distance from the ecliptic ; for 
whereas a star in the zodiac will appear to sweep the whole 
circumference of the heavens in an equinoctial year, a star situ- 
ated within the polar circle will describe only a very small circle 
in that period, and by so much the less, as it approaches the 
pole. The north pole of the Earth being elevated 23° 27-^-' 
towards the tropic of Cancer, the circumpolar stars will be suc- 
cessively at the least distance from it, when their longitude is 
3 signs or 90°. 

588. The position of the north polar star in 1855, was in the 
17° of Taurus; when it arrives at the first degree of Cancer, 
which it will do in about 250 years, it will be at its nearest 
possible approach to the pole — namely, 29' 55". About 2900 
years before the commencement of the Christian era, Alpha Dra- 
conis, the third star of the Dragon's tail, was in the first degree 
of Cancer, and only 10' from the pole ; consequently it was then 
the pole star. After the lapse of 11,600 years the star Lyra, 
the brightest in the northern hemisphere, will occupy the position 
of a pole star, being then about 5 degrees from the pole ; 
whereas now its north polar distance is upward of 51°. 

The mean average precession from the creation (4004 B. C.) to the year 1800, is 
49".51455 ; consequently the equinoctial points have receded since the creation, 2s. 14° 8' 
27°. The longitude of the star Beta Arietis, was in 1820, 31° 27' 28" : Jleton, a famou3 
mathematician of Athens, who flourished 430 years before Christ, says, this star, in his 
time, was in the vernal equinox. If he is correct, then 31° 27' 2S", divided by 2250 years, 
the elapsed time, will give 50%° for the precession. Something, however, must be 
allowed for the imperfection of the instruments used at that day, and even until the six- 
teenth century. 

589. Since all the stars complete half .a revolution about the 
axis of the ecliptic in about 12,500 years, if the North Star be 
at its nearest approach to the pole 250 years hence, it will, 

What, then, is the real pole of the heavens ? 587. Where is the precession of the stars 
most apparent? Where least? When are the circumpolar stars nearest the tropic of 
Cancer, and why? 5SS. Where was the pole star in 1855? When will it be nearest 
the true pole? How near then? What said of Alpha Draconis? Of Lyra t Mean 
average recession for 5800 years? Amount? Longitude of Beta Arietta in 1820? Be- 
fore Christ 430 years, where ? Average of precession for these 2250 years ? 589. What 
further result of the revolution of the pole of the heavens ? What effect ? Where, then, 



278 



ASTRONOMY. 



12,500 years afterwards, be at its greatest possible distance 
from it, or about 41° above it : — That is, the star itself will 
remain immovable in its present position, but the pole of the 
Earth will then point as much below the pole of the ecliptic, as 
now it points above. This will have the effect, apparently, of 
elevating the present polar star to twice its present altitude, or 
47°. Wherefore, at- the expiration of half the equinoctial year, 
that point of the heavens which is now 1° 18' north of the zenith 
of Hartford, will be the place of the north pole, and all those 
places which are situated 1° 18' north of Hartford, will then 
have the present pole of the heavens in their zenith. 



OBLIQUITY OF THE ECLIPTIC. 

590. The inclination of the Earth's axis to the plane of the 
ecliptic causes the equinoctial to depart 23° 28' from the eclip- 
tic. This angle made by the equinoctial and the ecliptic is 
called the Obliquity of the Ecliptic. 



OBLIQUITY OF THE ECLIPTIC. 

B 



Let the line A A represent 
the axis of the Earth, and B B 
the poles or axis of the eclip- 
tic. Now if the line A A in- 
clines toward the plane of the 
ecliptic, or, in other words, 
departs from the line B B, to 
the amount of 23° 28', it is 
obvious that the plane of the 
equator, or equinoctial, will 
depart from the ecliptic to the 
same amount. This depar- 
ture, shown by the angles 
C C, constitute the obliquity 
of the ecliptic. 

591. Hitherto, we 
have considered these 
great primary circles 
in the heavens, as never varying their position in space, nor with 
respect to each other. But it is a remarkable and well-ascer- 
tained fact, that both are in a state of constant change. We 
have seen that the plane of the Earth's equator is constantly 
drawn out of place by the unequal attraction of the. Sun and 
Moon acting in different directions upon the unequal masses of 
matter at the equator and the poles ; whereby the intersection 
qf the equator with the ecliptic is constantly retrograding — thus 
producing the precession of the equinoxes. 

will the north pole be 12,500 years hence ? 590. What is the Obliquity of the Ecliptic ? 
591. Is this angle always the same ? What variation of the equinoctial? 




PRECESSION OF THE EQUINOXES. 279 

592. The displacement of the ecliptic, on the contrary, is pro- 
duced chiefly by the action of the planets, particularly of Jupi- 
ter and Yenus, on the Earth ; by virtue of which the plane of 
the Earth's orbit is drawn nearer to those of these two planets, 
and consequently, nearer to the plane of the equinoctial. The 
tendency of this attraction of the planets, therefore, is to dimi- 
nish the angle which the plane of the equator makes with that 
of the ecliptic, bringing the two planes nearer together ; and if 
the Earth had no motion of rotation, it would, in time, cause 
the two planes to coincide. But in consequence of the rotary 
motion of the Earth, the inclination of these planes to each other 
remains very nearly the same ; its annual diminution being scarcely 
more than three-fourths of one second of a degree. 

The obliquity of the ecliptic, at the commencement of the present century was, accord- 
ing to Baily, 23° 27' 56%", subject to a yearly diminution of 0".4755. According to Bes- 
sel, it was 23° 27' 54". 32, with an annual diminution of 0".46. At this date (1855), it is only 
about 23° 27' 29". Consequently, the angle is diminished about 27" in 55 years. This 
diminution, however, is subject to a slight semi-annual variation, from the same causes 
which produce the displacement of the plane of the ecliptic, in precession. 

593. The attraction of the Sun and Moon, also, unites with 
that of the planets, at certain seasons, to augment the diminu- 
tion of the obliquity, and at other times, to lessen it. On this 
account the obliquity itself is subject to a periodical variation ; 
for the attractive power of the Moon, which tends to produce a 
change in the obliquity of the ecliptic, is variable, while the diur- 
nal motion of the Earth, which tends to prevent the change from 
taking place, is constant. Hence the Earth, which is so nicely 
poised on her center, bows a little to the influence of the Moon, 
and rises again, alternately, like the gentle oscillations of a 
balance. This curious phenomenon is called Nutation (589). 

In consequence of the yearly diminution of the obliquity of the ecliptic, the tropics are 
slowly and steadily approaching the equinoctial, at the rate of little more than three- 
fourths of a second every year; so that the Sun does not now come so far north of the 
equator in summer, nor decline so far south in winter, by nearly a degree, as it must 
have done at the Creation. 

594. The most obvious effect of this diminution of the obli- 
quity of the ecliptic, is to equalize the length of our days and 
nights ; but it has an effect also to change the position of the 
stars near the tropics. Those which were formerly situated 
north of the ecliptic, near the summer solstice, are now found to 
be still farther north, and farther from the plane of" the ecliptic. 
On the contrary, those which, according to the testimony of the 

592. What displacement of the ecliptic, and by what caused? Effect of these causes? 
Amount of change annually ? Obliquity of the ecliptic in 1800? In 1855? 593. Diminution 
in 55 years? What is Nutation ? Its cause? What effect from this annual diminu- 
tion of obliquity? 594. What other effect? Will this diminution continue? What 



280 



ASTRONOMY. 



ancient astronomers, were situated south of the ecliptic, near the 
summer solstice, have approached this plane, insomuch that some 
are now either situated within it, or just on the north side of it. 
Similar changes have taken place with respect to those stars 
situated near the winter solstice. All the stars, indeed, partici- 
pated more or less in this motion, but less, in proportion to their 
proximity to the equinoctial. 

< It is important, however, to observe, that this diminution will not always continue. A 
time will arrive when this motion, growing less and less, will at length entirely cease, 
and the obliquity will, apparently, remain constant for a time ; after which it will gra- 
dually increase again, and continue to diverge by the same yearly increment as it before 
had diminished. This alternate decrease and increase will constitute an endless oscilla- 
tion, comprehended between certain fixed limits. Theory has not yet enabled us to 
determine precisely what these limits are, but it may be demonstrated from the constitu- 
tion of our globe, that such limits exist, and that they are very restricted, probably not 
exceeding 2° 42'. If we consider the effect of this ever-varying attribute in the system 
of the universe, it may be affirmed that the plane of the ecliptic never has coincided 
with the plane of the equator, and never will coincide with it. Such a coincidence, 
could it happen, would produce upon the Earth perpetual spring. 

595. The method used by astronomers to determine the 
obliquity of the ecliptic is, to take half the difference of the 
greatest and least meridian altitudes of the Sun. 

The following table exhibits the mean obliquity of the ecliptic for every ten years 
during the present century. 



1800 


23° 


27' 


54". 78 


1860 


23° 


27' 


27". 36 


1810 


23 


27 


50 .21 


1870 


23 


27 


22 .79 


1820 


23 


27 


45 .64 


1880 


23 


-27 


18 .22 


1830 


23 


27 


41 .07 


1890 


23 


27 


13 .65 


1840 


23 


27 


36 .50 


1900 


23 


27 


09 .08 


1850 


23 


27 


31 .93 


1910 


23 


27 


04 .52 



CHAPTER XIII. 

PHILOSOPHY OF THE TIDES. 



596. Tides are the alternate rising and falling of the waters 
of the ocean, at regular intervals. Flood tide is when the waters 
are rising ; and ebb tide, when they are falling. The highest 
and lowest points to which they go are called, respectively, high 
and low tides. The tides ebb and flow twice every twenty-four 
hours — i. e., we have two flood and two ebb tides in that time. 



cycle of oscillation ? Its probable limits? What conclusion from this oscillation of the 
ecliptic? . 595. By what method do astronomers determine the obliquity of the ecliptic? 
596. What are tides? Flood and ebb tides? High and low? How often do they ebb 
and flow ? 



PHILOSOPHY OF THE TIDES. 



281 




59T. The tides are not uniform, either as to time or amount. 
They occur about 50 minutes later every day (as we shall 
explain hereafter), and sometimes rise much higher and sink 
much lower than the average. These extraordinary high and 
low tides are called, respectively, spring and neap tides. 

598. The cause of the tides is the attraction of the Sun and 
Moon upon the water of the ocean. But for this foreign influ- 
ence, as we may call it, the waters having found their proper 
level, would cease to heave and swell, as they now N0 TIDB 
do, from ocean to ocean, and would remain calm A 
and undisturbed, save by their own inhabitants and 
the winds of heaven, from age to age. 

In this figure, the Earth is represented as surrounded by water, in a 
state of rest or equilibrium, as it would be were it not acted upon by 
the Sun and Moon. 

599. To most minds, it would seem that the natural effect of 
the Moon's attraction would be to produce a single tide-wave 
on, the side of the Earth toward the Moon. It is easy, there- 
fore, for students to conceive how the Moon can produce one 
flood and one ebb tide in twenty four hours. 

In this cut, the Moon is shown at a distance above the Earth, and one tide-wave. 
attracting the waters of the ocean, so as to produce a high tide at A. 
But as the moon makes her apparent westward revolution around the 
Earth but once a day, the simple rising of a flood tide on the side of the 
Earth toward the moon, would give give us but one flood and one ebb 
tide in twenty-four hours ; whereas it is known that we have two of 
each. 

" The tides," says Dr. Herschel, " are a subject on which many per- 
sons find a strange difficulty of conception. That the Moon by her 
attraction, should heap up the waters of the ocean under her, seems to 
many persons very natural. That the same cause should, at the same 
time, heap them up on the opposite side of the Earth (viz., at B in the 
figure), seems to many palpably absurd. Yet nothing is more true." 

600. Instead of a single tide-wave upon the waters TW0 tide-waves. 
of the globe, directly under the Moon, it is found 
that on the side of the Earth directly opposite, 
there is another high tide ; and that half-way 
between these two high tides are two low tides. 
These four tides, viz., two high and two low, 
traverse the ocean from east to west every day, 
which accounts for both a flood and an ebb tide 
every twelve hours. 

597. Are the tides uniform? What variation of time? As to amount? What are 
these extraordinary high and low tides called? 598. The cause of tides? How but 
for this influence? 599. What most obvious effect of the Moon's attraction? Substance 
of note? Remark of Dr. Herschel? 600. How many tide-waves are there on the 
globe, and how situated ? 



D 





282 ASTRONOMY. 

In this cut, we have a representation of the tide-waves as they actually exist, except 
that their height, as compared with the magnitude of the Earth, is vastly too great. 
It is designedly exaggerated, the better to illustrate the principle under consideration. 
While the Moon at A attracts the waters of the ocean, and produces a high tide at B, 
we see another high tide at on the opposite side of the globe. At the same time it is 
low tide at D and E. 

601. The principal cause of the tide-wave on the side of the 
Earth opposite the Moon is the difference of the Moon's attrac- 
tion on different sides of the Earth. 

If the student well understands the subject of gravitation, he will easily perceive 
how a difference of attraction, as above described, would tend to produce an elongation 
of the huge drop of water called the Earth. The diameter of the Earth amounts to about 
— L-th of the Moon's distance ; so that, by the rule (558), the difference in her attraction 
on the side of the Earth toward her, and the opposite side, would be about yVth. The 
attraction being stronger at B (in the last cut) than at the Earth's center, and stronger 
at her center than at C, would tend to separate these three portions of the globe, giving 
the waters an elongated form, and producing two opposite tide-waves, as shown in 
the cut. 

602. A secondary cause of the tide-wave on the side of the 
Earth opposite the Moon, is the revolution of the Earth around 
the common center of gravity between the Earth and Moon, 
thereby generating an increased centrifugal force on that side 
of the Earth. 

The center of gravity between the Earth and Moon'is the point where they would 
exactly balance each other, if connected by a rod, and poised upon a fulcrum. 

CENTER OF GRAVITY BETWEEN THE EARTH AND MOON. 




This point which, according to Ferguson, is about 6000 miles from the Earth's center, 
is represented at A in the above, and also in the next cut. 

SECONDARY CAUSE OF HIGH TIDE OPPOSITE THE MOON. 



The point A represents the center of gravity between the Earth and Moon ; and as it 
is this point which traces the regular curve of the Earth's orbit, it is represented in the 
arc of that orbit, while the Earth's center is 6000 miles one side of it. Now, the law of 
gravitation requires that while both the Moon and Earth revolve around the Sun, they 
should also revolve around the common center of gravity between them, or ai'ound the 
point A. This would give the Earth a third revolution, in addition to that around the 

601. State the principal cause of the wave opposite the Moon? Demonstrate by dia- 
gram. 602. What other cause operates with the one just stated to produce the tide- 
wave opposite the Moon ? What is the center of gravity between the Earth and the 
Moon ? Where is it situated ? Illustrate the operation of this secondary cause. 



TIDE-WAVES BEHIND THE MOON. 



PHILOSOPHY OF THE TIDES. 283 

Sun and on her axis. The small circles show her path around the center of gravity, and 
the arrows her direction. 

This motion of the Earth would slightly increase the centrifugal tendency a± B, and 
thus help to raise the tide-wave opposite the Moon. But as this motion is slow, corre- 
sponding with the revolution of the Moon around the Earth, the centrifugal force could 
not be greatly augmented by such a cause. 

603. As the Moon, which is the principal cause of the tides, 
is revolving eastward, and comes to the meridian later and later 
every night, so the tides are about 50 minutes later each success- 
ive day. This makes the interval between two successive high 
tides 12 hours and 25 minutes. Besides 
this daily lagging with the Moon, the 
highest point of the tide-wave is found 
to be about 46° behind, or east of the //^ 

Moon, so that high tide does not / 

occur till about three hours after the 

Moon has crossed the meridian. The "^^iPt^N 

waters do not at once yield to the im- i8fcft^i&wV 

pulse of the Moon's attraction, but ^09$% 

continue to rise after she has passed ^^zyg^s 

over. 

In the cut, the Moon is on the meridian, but the highest point of the wave is at A, or 
45° east of the meridian ; and the corresponding wave on the opposite side at B is equally 
behind. 

604. The time and character of the tides are also affected by 
winds, and by the situation of different places. Strong winds 
may either retard or hasten the tides, or may increase or diminish 
their height ; and if a place is situated on a large bay, with but 
a narrow opening into the sea, the tide will be longer in rising, 
as the bay has to fill up through a narrow gate. Hence it is 
not usually high tide at New York till eight or nine hours after 
the Moon has passed the meridian. 

605. As both the Sun and Moon are concerned in the produc- 
tion of tides, and yet are constantly changing their positions 
with respect to the earth and to each other, it follows that they 
sometimes act against each other, and measurably neutralize each 
other's influence ; while at other times they combine their forces, 
and mutually assist each other. In the latter case, an unusually 
high tide occurs, called the Spring Tide. This happens both at 
new and full Moon. 

603. What daily lagging of the tides? Interval between two successive high tides? 
What other lagging? Cause of this last? 604. What modification of the time and 
character of the tides? 605. Do the Sun and Moon always act together in attracting 
the waters ? Why not ? How affect each other's influence ? Effect on the tides ? What 
are Spring Tides? When do they occur? Illustrate by diagram the cause of spring 
tides, when the Sun and Moon are in conjunction. 



284 



ASTRONOMY. 



CAUSE OF SPRING TIDES. 




**. "\ / 



M'WM'% 




Here the Sun and Moon, being in conjunction, unite their forces to produce an extra- 
ordinary tide. The same effect follows when they are in opposition ; so that we have 
two spring tides every month — namely, at new and full Moon. 

If the tide-waves at A and B are one-third higJier at the Moon's quadrature than usual, 
those of C and D will be one-third lower than usual. 

606. When the Moon is in quadrature, and her influence is 
partly neutralized by the Sun, which now acts against her, the 
result is a very low tide, called Neap Tide. 




f*P ■?!%/ 



^° S ^£ 



&N*X 



&***£ 



SPRING AND NEAP TIDES. 

The whole philosophy of spring and 
neap tides may be illustrated by the an- 
nexed diagram. 

On the right side of the cut, the Sun 
and Moon are in conjunction, and unite 
to produce a spring tide. 

At the first quarter, their attraction 
acts at right angles, and the Sun, instead 
of contributing to the lunar tide-waves, 
detracts from it to the amount of his 
own attractive force. The tendency to 
form a tide of his own, as represented in 
the figure, reduces the Moon's wave to 
the amount of one-third. 

At the full Moon, she is in opposition 
to the Sun, and their joint attraction 
acting again in the same line, tends to 
elongate the fluid portion of the Earth, V 

and a second spring tide is produced. 

Finally, at the third quarter, the Suu 
and Moon act against each other again, 
and the second neap tide is the result. 
Thus we have two spring and two neap 
tides during every lunation — the former 
at the Moon's cyzygies, and the latter at her quadratures. 

601. Although the Sun attracts the Earth much more power- 
fully, as a whole, than the Moon does, still the Moon contributes 
more than the Sun to the production of tides. Their relative 
influence is as one to three. The nearness of the Moon makes 




^apx^/ 



606. What are Neap Tides? Their cause ? Illustrate entire philosophy by diagram. 
607. Comparative influence of Sun and Moon in the production of tides ? Why Moon's 
influence the greatest? Substance of note ? Demonstration? 



PHILOSOPHY OF THE TIDES. 



285 



the difference of her attraction on different sides of the Earth 
much greater than the difference of the Sun's attraction on dif- 
ferent sides. 

It must not be forgotten that the tides are the result not so much of the attraction of 
the Sun and Moon, as a whole, as of the difference in their attraction on different sides 
of the Earth, caused by a difference in the distances of the several parts. The attrac- 
tion being inversely as the square of the distance (558), the influence of the Sun and 
Moon, respectively, must be in the ratio of the Earth's diameter to their distances. Now 



Moon's distance ; as 240,000+8,000= 



:30 ; while the difference, as compared with the dis- 
as 95,000,000+8,000=11,875. 

608. The tides are subject to another periodic variation, 
caused by the declination of the Sun and tides afpbcted bt declina . 
Moon north and south of the equator. 
As the tendency of the tide-wave is to 
rise directly under the Sun and Moon, 
when they are in the south, as in winter, 
or in the north, as in summer, every 
alternate tide is higher than the interme- 
diate one. 



■€>■ 



«.. 




At the time of the equinoxes, the Sun being over the 
equator, and the Moon within 5%° of it, the crest of the 
great tide-wave will be on the equator; but as the Sun 
and Moon decline south to A, one tide-wave forms in the 
south, as at B, and the opposite one in the north, as at 

C. If the declination was north, as shown at D, the order of the tides would be reversed. 
The following diagram, if carefully studied, will more fully illustrate the subject of the 
alternate high and low tides, in high latitudes, in winter and summer : 



ALTERNATE HIGH AND LOW TIDES. 




Let the line A A represent the plane of the ecliptic, and B B the equinoctial. On the 
21st of June, the day tide-wave is north, and the evening wave south, so that the tide 
following about three hours after the Sun and Moon, will be higher than the intermediate 
one at 3 o'clock in the morning. 

On the 23d of December, the Sun and Moon being over the southern tropic, the 
highest wave in the southern hemisphere will be about 3 o'clock P. M , and the lowest 
about 3 o'clock A.M.; while at the north, this order will be reversed. It is on this 
account that in high latitudes every alternate tide is higher than the intermediate ones ; 
the evening tides in summer exceeding the morning tides, and the morning tides in win- 
ter exceeding those of evening. 

609. All spring and neap tides are not alike as to their eleva- 
tion and depression. As the distances of the Sun and Moon are 



608. What other periodic variations mentioned? Explain cause, and illustrate. 
609. Are all spring and neap tides alike ? By what are they modified ? Illustrate by 
diagram. 



286 



ASTRONOMY. 



varied, so are the tides varied, especially by the variations of 
the Moon. 



VARIATIONS IN THE SPRING TIDES. 





If < ""% //U 

?\ 

At A, the Earth is in aphelion, and the Moon in apogee. As both the Sun and Moon 
are at their greatest distances, the Earth is least affected by their attraction, and the 
spring tides are proportionately low. 

At B, the Earth is in perihelion, and the Moon in perigee; so that both the Snn and 
Moon exert their greatest influence upon our globe, and the spring tides are highest, aa 
shown in the figure. In both cases, the Sun and Moon are in conjunction, but the varia- 
tion in the distances of the Sun and Moon causes variations in the spring tides. 

610. In the open ocean, especially the Pacific, the tide rises 
and falls but a few feet ; but when pressed into narrow bays 
or channels, it rises much higher than under ordinary cir- 
cumstances. 

The average elevation of the tide at several points on our coast is as follows : 

Cumberland, head of the Bay of Fundy 71 feet. 

Boston 11 }£ " 

New Haven 8 " 

New York 5 " 

Charleston, S. C 6 " 

611. As the great tide-waves proceed from east to west, they 
are arrested by the continents, so that the waters are per- 
manently higher on their east than on their west sides. The 
Gulf of Mexico is 20 feet higher than the Pacific Ocean, on the 
other side of the Isthmus ; and the Red Sea is 30 feet higher 
than the Mediterranean. Inland seas and lakes have no per- 
ceptible tides, because they are too small, compared with the 
whole surface of the globe, to be sensibly affected by the attrac- 
tion of the Sun and Moon. 

ATMOSPHERICAL TIDES. 

612. Air being lighter than water, and the surface of the 
atmosphere being nearer to the Moon than the surface of the 
sea, it cannot be doubted but that the Moon raises much higher 

610. Height of tides in open seas? How in narrow bays and channels? Height at dif- 
ferent points on our coast ? 611. Direction of tide-waves? What result? Instances 
cited ? Have inland seas and lakes any tides ? Why not ? Remarks respecting phi- 
losophy of tides ? 612. Atmospheric tides ? 



THE SEASONS. 287 

tides in the atmosphere than in the sea. According to Sir 
John Herschel these tides are, by very delicate observations, 
rendered not only sensible, but measurable. 

Upon the supposition that there is water on the surface of the Moon of the same 
specific gravity as our own, we might easily determine the height to which the Earth 
would raise a lunar tide, by the known principle, that the attraction of one of these 
bodies on the other's surface is directly as its quantity of matter, and inversely as its 
diameter. By mating the calculation, we shall find the attractive power of the Earth 
upon the Moon to be 21,777 times greater than that of the Moon upon the Earth. 

613. We have thus stated the principal facts connected with 
this complicated phenomenon, and the causes to which they are 
generally attributed. And yet it is not certain that the philoso- 
phy of tides is to this day fully understood. La Place, the great 
French mathematician and astronomer, pronounced it one of the 
most difficult problems in the whole range of celestial mechanics. 
It is probable that the atmosphere of our globe has its tides, as 
well as the waters ; but we have no means, as yet, for definitely 
ascertaining the fact 



CHAPTER XIY. 



THE SEASONS— D1FFEKENT LENGTHS OF THE DAYS AND 
NIGHTS. 

614. The vicissitudes of the seasons, and the unequal lengths 
of the days and nights, are occasioned by the annual revolution 
of the Earth around the Sun, with its axis inclined to the plane 
of its orbit. The temperature of any part of the Earth's sur- 
face depends mainly, if not entirely, upon its exposure to the 
Sun's rays. 

INCLINATION OF THE EARTH'S AXIS TO THE PLANE OF THE ECLIPTIC. 



615. Whenever the Sun is above the horizon of any place, 
that place is receiving heat ; when the Sun is below the horizon 
it is parting with it, by a process which is called radiation. The 
quantities of heat thus received and imparted in the course of 
the year, must balance each other at every place, or the equi- 

613. Is it certain that this subject is even yet well understood? Remark of Laplace? 
614. Cause of the seasons, and the unequal length of the days and nights? Temperature 
of the Earth ? 615. When does any place gain heat, and when lose ? Upon what does 



283 



ASTRONOMY. 



librium of temperature would not be supported. Whenever the 
Sun remains more than twelve hours above the horizon of any 
place, and less beneath, the general temperature of that place 
will be above the mean state ; when the reverse takes place, the 
temperature, for the same reason, will be below the mean state. 
Now, the continuance of the Sun above the horizon of any place, 
depends entirely upon his declination, or altitude at noon. 

616. About the 20th of March, when the Sun is in the ver- 
nal equinox, and consequently has no declination, he rises at six 
in the morning and sets at six in the evening ; the day and night 
are then equal, and as the Sun continues as long above our 
horizon as below it, his influence must be nearly the same at the 
same latitudes, in both hemispheres. 

From the 20th of March to the 21st of June, the days grow 
longer, and the nights shorter, in the northern hemisphere ; the 
temperature increases, and we pass from spring to midsummer ; 
while the reverse of this takes place in the southern hemisphere. 

From the 21st of June to the 23d of September, the days 
and nights again approach to equality, and the excess of tem- 
perature in the northern hemisphere above the mean state, grows 
less, as also its defect in the southern ; so that, when the Sun 
arrives at the autumnal equinox, the mean temperature is again 
restored. 



61?. From the 23d of 
September until the 21st of 
December, our nights grow 
longer and the days shorter, 
and the cold increases as 
before it diminished, while 
we pass from autumn to 
mid-winter, in the northern 
hemisphere, and the inhabit- F 
ants of the southern hemi- 
sphere from spring to mid- 
summer. 

From the 21st of Dec. 
to the 20th of March, the 
cold relaxes as the days grow 
longer, and we pass from 



CAUSE OF THE SEASONS. 
B 



U-" 



/,UTU';MNAL 



EJJU 



':N0X 



\ SEP/H-23 





the length of the days depend? 616. How ah out the 20th of March? From March 
20th to June 21st ? From June 21st to September 23d ? 617. From September 23d to 
December 21st? From December 21st to March 20th? How with the seasons in the 



THE SEASONS. 289 

the dreariness of winter to the mildness of spring, when the 
seasons are completed, and the mean temperature is again 
restored. The same vicissitudes transpire, at the same time, in 
the southern hemisphere, but in a contrary order. Thus are 
produced the four seasons of the year. 

In the preceding cut, the Earth is shown in her orbit, with her axis inclined 235^ ° ; the 
North Pole being towards the eye of the student. At A and B the Sun shines from pole 
to pole, and the days and nights are equal in both hemispheres. On the right, the North 
Pole is in the light, and we have summer in the northern hemisphere. On the left, the 
reverse is the case. And the gradual shortening or lengthening of the days, and the 
change of temperature, are produced by the passage of the Earth from one point to 
another, with her axis thus inclined. 

618. But I have stated not the only, nor, perhaps, the most 
efficient cause in producing the heat of summer and the cold of 
winter. If, to the inhabitants of the equator, the Sun were to 
remain 1 6 hours below their horizon, and only 8 hours above it, 
for every day of the year, it is certain they would never expe- 
rience the rigors of our winter ; since it can be demonstrated, 
that as much heat falls upon the same area from a vertical Sun 
in 8 hours, as would fall from him, at an angle of 60°, in 16 
hours. 

Now, as the Sun's rays fall most ohliquely when the days are 
shortest, and most directly when the days are longest, these two 
causes — namely, the duration and intensity of the solar heat, 
together, produce the temperature of the different seasons. The 
reason why we have not the hottest temperature when the days 
are longest, and the coldest temperature when the days are 
shortest, but in each case about a month afterwards, appears to 
be, that a body once heated, does not grow cold instantaneously, 
but gradually, and so of the contrary. Hence, as long as more 
heat comes from the Sun by day than is lost by night, the heat 
will increase, and vice versa. 

BEGINNING AND LENGTH OF THE SEASONS. 

h. m. s. 

Sun enters \3 (Winter begins) 1849, December 21, 7 25 46 M. T. Wash. 
" " f (Spring " ) 1850, March 20, 8 56 38 " " 
« " © (Summer " ) " June 21, 6 3 9 " " 

" " =s= (Autumn " ) " Sept. 22, 19 58 21 » " 

" " -V3 (Winter " ) " December 21, 13 21 57 " " 

southern hemisphere ? 618. Is the simple fact that a place is enlightened by the Sun, a 
sufficient cause for its being warm? What circumstance determines the intensity of the 
Sun's rays ? Why, then, is it not warmest during the longest days, and on the contrary 
coldest during the shortest days? How long will heat increase ? 



290 ASTRONOMY. 



d. h. m. b. 

Sun in the Winter Signs . . . . 89 1 30 52 

" Spring 92 21 6 31 

" Summer 93 13 55 22 

" Autumn 89 IT 23 26 

north of Equator (Spring and Summer) 186 11 1 53 

south " (Winter and Autumn) 178 18 54 18 



Longest north of the Equator . . 7 16 7 35 

Length of the tropical year beginning at ) 

the winter solstice 1849, and ending at v 365 5 56 11 

the winter solstice 1850. ) 

Mean or average length of the tropical year, 365 5 48 48 



619. The north pole of the Earth is denominated the elevated 
pole, because it is always about 23^-° above a perpendicular to 
the plane of the equator, and the south pole is denominated the 
depressed pole, because it is about the same distance below such 
perpendicular. 

As the Sun cannot shine on more than one-half the Earth's surface at a time, it is 
plain, that when the Earth is moving through that portion of its orbit which lies above 
the Sun, the elevated pole is in the dark. This requires six months, that is, until the 
Earth arrives at the equinox, when the elevated pole emerges into the light, and the 
depressed pole is turned away from the Sun for the same period. Consequently, there 
are six months day and six months night, alternately, at the poles. 

620. When the Sun appears to us to be in one part of the 
ecliptic, the Earth, as seen from the Sun, appears in the point 
diametrically opposite. Thus, when the Sun appears in the ver- 
nal equinox at the first point of Aries, the Earth is actually in 
the opposite equinox at Libra. The days and nights are then 
equal all over the world. (See the cut, pages 288 and 292.) 

As the Sun appears to move up from the vernal equinox to the summer solstice, the 
Earth actually moves from the autumnal equinox down to the winter solstice. The days 
now lengthen in the northern hemisphere, and shorten in the southern. The Sun is now 
over the north pole, where it is mid-day, and opposite the south pole, where it is midnight. 

As the Sun descends from the summer solstice towards the autumnal equinox, the Earth 
ascends from the winter solstice towards the vernal equinox. The summer days in the 
northern hemisphere having waxed shorter and shorter, now become again of equal 
length in both hemispheres. 

621. While the Sun apears to move from the autumnal equi- 
nox down to the winter solstice, the Earth passes up from the 
vernal equinox to the summer solstice ; the south pole comes 
into the light, the winter days continually shorten in the northern 
hemisphere, and the summer days as regularly increase in length 
in the southern hemisphere. 

While the Sun appears again to ascend from its winter solstice 
to the vernal equinox, the Earth descends from the Summer 
solstice to the autumnal equinox. The summer days now shorten 

619. Which is the elevated pole, and why? The depressed, and why? How are the 
seasons produced? 620. How are the Earth and Sun situated in the ecliptic, with 
reference to each other? What said of the Sun's apparent motion around the zodiac? 
621. What further description of the Sun's apparent progress ? 



THE SEASONS. 291 

in the southern hemisphere, and the winter days lengthen in the 
northern hemisphere. 

622. When the Sun passes the vernal equinox, it rises to the 
arctic or elevated pole, and sets to the antarctic pole. When 
the Sun arrives at the summer solstice, it is noon at the north 
pole, and midnight at the south pole. When the Sun passes the 
autumnal equinox, it sets to the north pole, and rises to the 
south pole. When the Sun arrives at the winter solstice, it is 
midnight at the north pole, and noon at the south pole ; and 
when the Sun comes again to the vernal equinox, it closes the 
day at the south pole, and lights up the morning at the north 
pole. 

There would, therefore, be 186-J- days during which the Sun 
would not set at the north pole, and an equal time during which 
he would not rise at the south pole ; and 118-J- days in which he 
would not set at the south pole, nor rise at the north pole. 

623. At the arctic circle, 23° 2TJ-' from the pole, the longest 
dav is 24 hours, and goes on increasing as you approach the 
pole. In latitude 6?° 18' it is 30 days ; in lat. 69° 30' it is 60 
days, &c. The same takes place between the antarctic circle 
and the south pole, with the exception, that the day in the same 
latitude south is a little shorter, since the Sun is not so long 
south of the equator, as at the north of it. In this estimate no 
account is taken of the refraction of the atmosphere, which, as 
we shall see hereafter, increases the length of the day, by mak- 
ing the Sun appear more elevated above the horizon than it 
really is. All these apparent motions of the Sun are due to the 
inclination of the Earth's axis (or the obliquity of the ecliptic), 
and her revolution around the Sun. 

The following cut represents the inclination of the Earth's axis to its orbit in every 
one of the twelve signs of the zodiac, and consequently for each month in the year. 
It is such a view as a beholder would have, situated in the north pole of the ecliptic, at 
some distance from it, and consequently, is a perpendicular view, the north pole of the 
Earth being towards us. The Sun enters the sign Aries, or the vernal equinox, on the 
20th of March, when the Earth enters Libra, and when her axis inclines neither towards 
the Sun, nor from it, but stands exactly sideways to it ; so that the Sun then shines 
equally upon the Earth from pole to pole, and the days and nights are everywhere equal. 
This is the beginning of the astronomical year; it is also the beginning of day at the 
north pole, which is just coming into light and the end of day at the south pole, which 
is just going into darkness. 

By the Earth's orbitual progress, the Sun appears to enter the second sign, Tawfus, 
on the 20th of April, when the north pole has sensibly advanced into the light, while the 
south pole has been declining from it ; whereby the days become longer than the nights 
in the northern hemisphere, and shorter in the southern. 

On the 21st of May, the Sun appears to enter the sign Gemini, when the north pole 

622. How are the light and darkness of the poles affected by the Sun's apparent motion ? 
623. What said of the length of the days within the arctic circle ? In latitude 6T° 18' ? 
In latitude 69° 80'? How at the other pole? To what are these various apparent 
motions of the Sun really due ? 

B.G. 13 



292 



ASTRONOMY. 



has advanced considera- philosophy op the seasons.* i 

bly further into the light, 

while the south pole has 

proportionally declined 

from it; the summer 

days are now waxing 

longer in the northern 

hemisphere, and the 

nights shorter. 

The 21st of June, when 
the Sun enters the sign 
Cancer, is the first day 
of summer in the astro- 
nomical year, and the 
longest day in the north- 
ern hemisphere. The 
north pole now has its 
greatest inclination to 
the Sun, the light of 
which, as is shown by 
the boundary of light and 
darkness, in the figure, 
extends to the utmost 
verge of the Arctic Cir- 
cle ; the whole of which 
is included in the enlight- 
ened hemisphere of the 
Earth, and enjoys, at 
this season, constant day 
during the complete revo- 
lution of the Earth on its 

axis. The whole of the Northern Frigid Zone is now in the circle of perpetual illumi- 
nation. 

On the 23d of July, the Sun enters the sign Leo, and as the line of the Earth's axis always 
continues parallel to itself, the boundary of light and darkness begins to approach nearer 
to the poles, and the length of the day in the northern hemisphere, which had arrived 
at its maximum, begins gradually to decrease. On the 23d of August, the Sun enters the 
sign Virgo, increasing the appearances mentioned in Leo. 

On the 23d of September, the Sun enters Libra, the first of the autumnal signs, when 
the Earth's axis having the same inclination as it had in the opposite sign, Aries, is 
turned neither from the Sun, nor towards it, but obliquely to it, so that the Sun again 
now shines equally upon the whole of the Earth's surface from pole to pole. The days 
and nights are once more of equal length, throughout the world. 

On the 23d of October, the Sun enters the sign Scorpio ; the days visibly decrease 
in length in the northern hemisphere, and increase in the southern. 

On the 22d of November the Sun enters the sign Sagittarius, the last of the autumnal 
signs, at which time the boundary of light and darkness is at a considerable distance 
from the north pole, while the south pole has proportionally advanced into the light ; the 
length of the day continues to increase in the southern hemisphere, and to decrease in 
the northern. 

On the 21st of December, which is the period of the winter solstice, the Sun enters the 
sign Capricorn. At this time, the north pole of the Earth's axis is turned from the 
Sun, into perpetual darkness ; while the south pole, in its turn, is brought into the light 
of the Sun, whereby the whole Antarctic region comes into the circle of perpetual illumi- 
nation. It is now that the southern hemisphere enjoys all those advantages with which 
the northern hemisphere was favored on the 21st of June ; while the northern hemi- 
sphere, in its turn, undergoes the dreariness of winter, with short days and long 
nights. 




* This diagram and the accompanying explanations should be carefully studied till 
they are thoroughly understood by the learner. The cause of the seasons and of the 
unequal lengths of the days and nights, is a matter of which no professedly educated 
person ought to be ignorant, or to entertain confused and indefinite notions. By all 
means let this point be studied till the student can tell the cause of every particular phe- 
nomenon of the seasons and the length of the days, without any particular interro- 
gation. 



THE HARVEST MOON AND HORIZONTAL MOON. 293 

624. By carefully observing the figure, it may be seen that 
the orbit of the Earth is slightly elliptical, that the Sun is to 
the left of the center, and that consequently, the Earth is nearer 
the Sun on the 21st of December, than on the opposite side of 
the ecliptic, on the 21st of June. This may seem strange to the 
learner, that we should have our winter when nearest the Sun, 
and our summer when most distant ; but it must be remembered 
that the temperature of any particular part of the Earth is 
not so much affected by the distance of the Sun, as by the direct- 
ness or obliquity of his rays. Hence, though we are farther 
from the Sun on the 21st of June than on the 21st of December, 
yet, as the north pole of the Earth is turned more directly into 
the light at that time, so that the Sun's rays strike her surface 
less obliquely than in December, we have a higher temperature 
at that period, though at a greater distance from the Sun. 

625. The difference, however, between the aphelion and peri- 
helion distances of the Earth is so slight, in comparison with the 
whole distance, as scarcely to cause a perceptible difference in the 
amount of light received at her respective positions. The eccen- 
tricity of the Earth's orbit, or the distance of the Sun from its 
center, is only about 1,618,000 miles, so that the variation is 
only 3,236,000 miles, or about one-thirtieth of the mean distance. 
The true orbit of the Earth could not be distinguished from a 
circle. 

The only effect of the eccentricity of the Earth's orbit upon her temperature is, that 
she has probably a greater degree of heat, during summer in the southern hemisphere, 
when the Earth is at her perihelion, than we ever have at the north in the same lati- 
tude. But this difference must be very slight, if indeed it is at all perceptible. 



CHAPTER XY. 

THE HAKYEST MOON AND HOEIZONTAL MOON. 

626. The daily progress of the Moon in her orbit, from west to 
east, causes her to rise, at a mean rate, 48 minutes and 44 
seconds later every day than on the preceding. But in places 
of considerable latitude, a remarkable deviation from this rule 



624. What said of the form of the Earth's orbit? When are we nearest the Sun? 
Why is it not then the warmest in the United States ? 625. What is the amount of the 
Earth's variation in distance from the Sun? What effect upon the light and heat of the 
Earth? 626. Subject of this chapter? Mean rate of the Moon's daily delay in rising? 



294 ASTRONOMY. 

takes place, especially about the time of harvest, when the full 
Moon rises to us for several nights together, only from 18 to 25 
minutes later in one day, than on that immediately preceding. 
From the benefit which her light affords, in lengthening out the 
day, when the husbandmen are gathering in the fruits of the 
Earth, the full Moon, under these circumstances, has acquired 
the name of Harvest Moon. 

It is believed that this fact was observed by persons engaged in agriculture, at a much 
earlier period than that in which it was noticed by astronomers. The former ascribed it 
to the goodness of the Deity ; not doubting but that he had so ordered it for their advan- 
tage. 

621. About the equator, the Moon rises throughout the year 
with nearly the equal intervals of 48f minutes ; and there the 
harvest Moon is unknown. At the polar circles, the autumnal 
full Moon, from her first to her third quarter, rises as the Sun 
sets ; and at the poles, where the Sun is absent during one-half 
of the year, the winter full Moons, from the first to the third 
quarter, shine constantly without setting. 

By this, it is not meant that the Moon continues full from her first to her third quar- 
ter; but that she never sets to the North Polar regions, when, at this season of the year, 
she is within 90° of that point in her orbit, where she is at her full. In other words, as 
the Sun illumines the south pole during one -half of its yearly revolution, so the Moon, 
being opposite to the Sun at her full, must illumine the opposite pole, during half of her 
revolution about the Earth. The phenomenon of the Harvest Moon may be thus exem- 
plified by means of the globe. 

Rectify the globe to the latitude of the place, put a patch or piece of wafer in the eclip- 
tic, on the point Aries, and mark every 12° preceding and following that point, to the 
number of ten or twelve marks on each side of it; bring the equinoctial point marked by 
the wafer to the eastern edge of the horizon, and set the index to 12 ; turn the globe 
westward till the other marks successively come to the horizon, and observe the hours 
passed over by the index ; the intervals of time between the marks coming to the horizon, 
will show the diurnal difference of time between the Moon's rising. If these marks be 
brought to the western edge of the horizon in the same manner, it will show the diurnal 
difference between the Moon's setting. 

From this problem it will also appear, that, when there is the least difference between 
the times of the Moon's rising, there will be the greatest cufference between the times of 
her setting, and the contrary. 

The reason why you mark every 12° is, that the Moon gains 12° 11' on the apparent 
course of the Sun every day, and these marks serve to denote the place of the Moon 
from day to day. It is true, this process supposes that the Moon revolves in the plane 
of the ecliptic, which is not the case ; yet her orbit so nearly coincides with the ecliptic 
(differing only 5° 9' from it), that they may, for the convenience of illustration, be con- 
sidered as coinciding ; that is, we may take the ecliptic for the representative of the 
Moon's orbit. 

628. The different lengths of the lunar night, at different lati- 
tudes, is owing to the different angles made by the horizon and 
different parts of the Moon's orbit ; or, in other words, by the 

What remarkable deviation ? What is the Moon then called, and why ? How anciently 
was this phenomenon observed? To what attributed? 627. Is the Harvest Moon 
known at the equator? How at the Polar circles ? At the poles? Does she there exhi- 
bit her usual phases ? Can you illustrate the phenomenon of the Harvest Moon by a 
globe 1 628. To what is the different lengths of the lunar nights attributable ? 



THE HARVEST MOON AND HORIZONTAL MOON. 295 

Moon's orbit lying sometimes more oblique to the horizon than 
at others. 

In the latitude of London, for example, as much of the ecliptic rises about Pisces and 
Aries in two hours as the Moon goes through in six days ; therefore, while the Moon is in 
these signs, she differs but two hours in rising for six days together ; that is, one day 
with another, she rises about 20 minutes later every day than on the preceding. 

629. The parts or signs of the ecliptic which rise with the 
smallest angles, set with the greatest ; and those which rise with 
the greatest, set with the least. And whenever this angle is 
least, a greater portion of the ecliptic rises in equal times than 
when the angle is larger. Therefore, when the Moon is in those 
signs which rise or set with the smallest angles, she rises or sets 
with the least difference of time ; but when she is in those signs 
which rise or set with the greatest angles, she rises or sets with 
the greatest difference of time. 

Let the globe, for example, be rectified to the latitude of New York, 40° 42' 40", with 
Cancer on the meridian, and Libra rising in the east. In this position, the ecliptic has a 
high elevation, making an angle with the horizon of 723*2°. 

But let the globe be turned half round on its axis, till Capricorn comes to the meridian, 
and Aries rises in the east, then the ecliptic will have a low elevation above the horizon, 
making an angle with it of only 25 j£ °. This angle is 47° less than the former angle, and 
is equal to the distance between the tropics. 

630. In northern latitudes, the smallest angle made by the 
ecliptic and horizon is when Aries rises ; at which time Libra 
sets ; the greatest is, when Libra rises and Aries sets. The eclip- 
tic rises fastest about Aries, and slowest about Libra. Though 
Pisces and Aries make an angle of only 25-J- with the horizon 
when they rise, to those who live in the latitude of New York, 
yet the same signs, when they set, make an angle of T2-J- . The 
daily difference of the Moon's rising, when in these signs, is, in 
New England, about 22 minutes ; but when she is in the oppo- 
site signs, Yirgo and Libra, the daily difference of her rising is 
almost four times as great, being about one hour and a quarter. 

.631. As the Moon can never be full but when she is opposite 
to the Sun, and the Sun is never in Yirgo or Libra except in 
our autumnal months, September and October, it is evident that 
the Moon is never full in the opposite signs, Pisces and Aries, 
except in those two months. We can, therefore, have only two 
full Moons in a year, which rise, for a week together, very near 
the time of sunset. The former of these is called the Harvest 
Moon, and the latter, the Hunter's Moon. 

629. What said of the angles under which the signs rise and set ? What result follows 
as to time of the Moon's rising and setting ? How illustrate by globe ? 630. When is 
the angle smallest in northern latitudes? When greatest? What difference of angle at 
the rising and setting of Pisces ? Daily difference of the Moon's rising ? When in Pisces 
and Aries ? What when in Virgo and Libra ? 631. Why have we not more than one 
Harvest, and one Hunter's Moon in a year ? 



296 ASTRONOMY. 

632. Although there can be but two full Moons in the year 
that rise with so little variation of time, yet the phenomenon 
of the Moon's rising for a week together so nearly at the same 
time, occurs every month, in some part of her course or the 
other. 

In Winter, the signs Pisces and Aries rise about noon ; hence the rising of the Moon 
is not then regarded nor perceived. 

In Spring, these signs rise with the Sun, because he is then in them ; and as the Moon 
changes while passing through the same sign with the Sun, it must then be the change, 
and hence invisible. 

In Summer, they rise about midnight, when the Moon, is in her third quarter. On 
account of her rising so late, and giving but little light, her rising passes unobserved. 

633. To the inhabitants at the equator, the north and south 
poles appear in the horizon, and therefore the ecliptic makes the 
same angle southward with the horizon when Aries rises, as it 
does northward when Libra rises ; consequently the Moon rises 
and sets not only with angles nearly equal, but at equal intervals 
of time, all the year round ; hence, there is no harvest Moon at 
the equator. The farther any place is from the equator, if it be 
not beyond the polar circles, the angle which the ecliptic makes 
with the horizon gradually diminishes when Pisces and Aries rise. 

634. Although, in northern latitudes, the autumnal full Moons 
are in Pisces and Aries ; yet in southern latitudes it is just the 
reverse, because the seasons are so : — for Yirgo and Libra rise 
at as small angles with the horizon in southern latitudes as Pisces 
and Aries do in the northern ; and therefore the harvest Moons 
are just as regular on one side of the equator as on the other. 

At the polar circles, the full Moon neither rises in summer, nor sets in winter. For the 
winter full Moon being as high in the ecliptic as the summer Sun, she must continue while 
passing through the northern signs, above the horizon ; and the summer full Moon, being 
as low in the ecliptic as the winter Sun, can no more rise, when passing through the 
southern signs, than he does. 

635. The great apparent magnitude of the Moon, and indeed 
of the Sun, at rising and setting, is a phenomenon which has 
greatly embarrassed almost all who have endeavored to account 
for it. According to the ordinary laws of vision, they should 
appear to be least when nearest the horizon, being then farthest 
from the eye ; and yet the reverse of this is found to be true. 
The apparent diameter of the Moon, when viewed in the horizon 
by the naked eye, is two or three times larger than when at the 
altitude of thirty or forty degrees ; and yet when measured by 
an instrument her diameter is not sensibly increased. 

632. Does not the Moon rise with little variation for several nights in succession, 
every month? Why not always perceived? 633. Why is there no Harvest Moon at 
the equator? 634. What said of these lunar phenomena in the Southern hemisphere? 
635. What said of the apparent diameter of the Moon in the horizon? How when 



REFRACTION AND TWILIGHT. 297 

Both the Sun and the Moon really subtend a greater angle when on the meridian, than 
they do in the horizon ; because they are then actually nearer the place of the spectator 
by the whole semi-diameter of the Earth ; and one reason why they appear largest in 
the horizon is, that they are then compared with terrestrial objects, with whose magni- 
tude we are acquainted. 

This apparent increase of magnitude in the horizontal Moon, is chiefly an optical illu- 
sion, produced by the concavity of the heavens appearing to the eye to be a less portion 
of a spherical surface than a hemisphere. The eye is accustomed to estimate the dis- 
tance between any two objects in the heavens by the quantity of sky that appears to lie 
between them; as upon the Earth we estimate it by the quantity of ground that lies 
between them. Now when the Sun or Moon is just emerging above the eastern horizon, 
or sinking beneath the western, the distance of the intervening landscape over which 
they are seen, contributes, together with the refraction of the atmosphere, to exaggerate 
our estimate of their real magnitudes. 

THE HORIZONTAL MOON. 

636. Both the Sun and Moon are sometimes seen to be elon- 
gated horizontally, when near the horizon. This is often the case 
when the atmosphere is very dense. The cause of this pheno- 
menon is this : All celestial bodies in the horizon are more or 
less elevated by atmospherical refraction (See page 300) ; and 
the amount of this apparent elevation depends somewhat upon 
the density of the atmosphere as well as upon the altitude of the 
object. When, therefore, the Sun or Moon are near the horizon, 
and viewed through a dense atmosphere, the refraction is great- 
est ; and as their lower limb is seen through a denser stratum of 
atmosphere than their upper limb, its apparent elevation is 
greater, and the object seems to he flattened, while its horizontal 
diameter is not sensibly diminished. 

This phenomenon and its cause may be easily illustrated by a diagram. 



CHAPTER XYI. 

REFRACTION AND TWILIGHT. 

631. The rays of light, in passing out of one medium into 
another of a greater density, deviate from a straight course, and 
are bent towards a perpendicular to that course ; and if the 
density of the latter medium continually increase, the rays of 

measured ? When do they subtend the greater angle ? Why appear largest when in 
the horizon? What other explanation given ? 636. What is meant by a Horizontal 
Moon? The cause of this phenomenon? 637. What is meant by the refraction of 
light? What principles govern it? 



298 



ASTRONOMY. 



LIGHT REFRACTED BY WATER. 
D G A 



light in passing through it, will deviate more and more from a 
right line as they pass downwards, or towards the eye of the 
observer. 

638. As air and water are both transparent, but of different 
densities, it follows that, when light passes obliquely from one 
to the other, it will be 
refracted. If it pass 
from the air into the 
water, it will be refract- 
ed towards a perpendicv^ 
lav. 

Here the ray A C strikes the 
water perpendicularly, and passes 
directly through to B without be- 
ing refracted. But the ray D C 
strikes the water at C obliquely ; 
and instead of passing straight 
through to E, is refracted at C, 
and reaches the bottom of the water at F. If, therefore, a person were to receive the 
ray into the eye at F, and to judge of the place of the object from which the light ema- 
nates from the direction of the ray C F, he would conclude that he saw the object at Gr, 
unless he made allowance for the refraction of the light at C. 




LIGHT PROCEEDING FROM WATER. 

B 




639. When light passes 
obliquely from a denser 
to a rarer medium, as 
from water into air, it is 
refracted from a perpen- 
dicular towards a horizon- 
tal. 

Here the lamp A shines up 
through water into air. The ray 
that strikes the surface perpen- 
dicularly passes on to B without 
oeing refracted ; but the other rays 
that leave the water obliquely are refracted toward a horizontal direction, in proportion 
to their distance from the perpendicular; or, in other words, in proportion to the 
obliquity of their contact with the surface of the water. 

640. In consequence of the refraction of light towards a hori- 
zontal direction, in passing from water into air, a pole, half of 
which is in the water, seems bent at the surface, and the lower 
end seems nearer the surface than it really is. For the same 
reason, the bottom of a river seems higher, if seen- obliquely, than 
it really is ; and the water is always deeper than we judge it 
to be. 



638. How refracted by air and water ? 639. How when light passes from denser to 
rarer media? 640. Effect of refraction upon objects seen under water? 



REFRACTION AND TWILIGHT. 



299 



In this cut, the oar, the blade of effect of rkfractios. 

Which is in the water, seems bent at the 
surface of the water. The rays of light 
passing from the part under water to 
the surface at D, are refracted toward 
a horizontal direction at that point, 
and received into the eye of the ob- 
server at B, who, judging of the posi- 
tion of the immersed portion of the oar 
from the direction of the rays D B, 
locates the blade of the oar at C ; thus 
reversing the effect illustrated at 
638. 

641. The refracting power of different transparent substances 
depends mainly upon their density. Water refracts more than 
air, glass more than water, and diamond most of all. But the 
angle of incidence, or the obliquity of the contact of the rays 
with the denser substance, has also much to do in determining 
the amount of refraction. 




EFFECT OF REFRACTION 



642. By the aid of refraction, 
we may see objects that are 
actually behind an opaque or 
intransparent body. 

Here the piece of money at A, at the 
bottom of the cup, would be invisible to 
the beholder at B, if the cup was empty, 
as the light from the money would pass 
from A to C ; but when the oup is filled 
with water, the light is refracted to B, and 
the beholder sees the money apparently 
at D. 



643. By the 
law of refrac- 
tion, light has 
been found to 
consist of a com- 
bination of co- 
lors. By pass- 
ing a beam of 
light through a Blue!.. 

. b . t c - Green.. 

triangular piece Yeiiow.. 

Of flint glaSS Orange, 
-n , & - Red 

called a prism, 
it is seen that 
parts of 




REFRACTION" BT A PRISM. 



Violet. 
Indigo. 



White- 




SOme 



641. Upon what does the refracting power of different transparent media depend? 
642. What other effect of refraction? 643. What discovery by refraction? How 

made? 



13* 



300 



ASTRONOMY. 



the light are more refrangible than others, so that the light is 
analyzed, or separated into its component parts or elements. 

Let a ray of light from the Sun be admitted through a hole in the window shutter, A, 
into a room from which all other light is excluded ; it will form on a screen placed a little 
distance in front, a circular image, B, of white light. Now interpose near the shutter a 
glass prism, C, and the light, in passing through it, will not only be refracted in the same 
direction, both when it enters the prism and when it leaves it, but the several rays of 
which white light is composed will be separated, and will arrange in regular order on the 
screen, immediately above the image B, which will disappear. The violet ray, it will be 
seen, is most refracted, and the red least; the whole forming on the scale an elongated 
image of the Sun, called the solar spectrum. — Johnston. 

644. It is the refraction of the clouds that gives the sky its 
beautiful colors morning and evening ; and the refracting power 
of the rain-drops produces the beautiful phenomenon of the rain- 
bow. 

ATMOSPHERICAL REFRACTION. 



645. The refracting power of the atmosphere produces many 
curious phenomena. Sometimes ships are seen bottom upwards 
in the air, single or double. At other times, objects really below 
the horizon, as ships or islands, seem to rise up, and to come dis- 
tinctly in view. 

646. A very important effect of refraction, as it relates to 
astronomy, is, that it more or less affects the apparent places of 
all the heavenly bodies. As the light coming from them strikes 
the atmosphere obliquely, and passes downward through it, it is 
refracted or bent towward the Earth, or toward a perpendicular. 
And as we judge of the position of the object by the direction 
of the ray when it enters the eye, we place objects higher in the 
heavens than they really are. 

ATMOSPHERICAL REFRACTION. 

Let A, in the cut, repre- 
sent the Earth ; B, the at- 
mosphere ; C C, the visible 
horizon ; and the exterior 
circle the apparent con- 
cave of the heavens. Now, 
as the light passes from 
the stars, and strikes the 
atmosphere, it is seen to 
curve downward, because 
it strikes the atmosphere 
obliquely ; and the air in- 
creases in density as we 
approach the Earth. But 
as the amount of refraction depends not only upon the density, but also upon the obli- 
quity of the contact, it is seen that the refraction is greatest at the horizon, and gradu- 
ally diminishes till the object reaches the zenith, when there is no obliquity, and the refrac- 




644. What other effects of refraction ? 645. Atmospherical refraction ? Effects on 
terrestrial objects ? C46. Upon apparent places of stars, &c. ? 



REFRACTION AND TWILIGHT. 301 

tion wholly ceases. The dark lines in the cut show the true, and the dotted the apparent 
positions. 

In the cut, the depth of the atmosphere, as compared with the globe, is greatly exag- 
gerated. Even allowing it to be 50 miles deep, it is only- L th of the semi-diameter of the 
globe, which is equal to only aboutj 3 ^-th of an inch upon a common 13-inch globe. But 
it was necesary to exaggerate, in order to illustrate the principle. 

647. The amount of displacement of objects in the horizon, 
by atmospherical refraction, is about 33', or a little more than 
the greatest apparent diameter of either the Sun or Moon. It 
follows, therefore, that when we see the lower edge of either 
apparently resting on the horizon, its whole disc is in reality below 
it ; and would be entirely concealed by the convexity of the 
Earth, were it not for refraction. 

648. Another effect of refraction is, that the Sun seems to 
rise about three minutes earlier, and to set about three minutes 
later, on account of atmospherical refraction, than it otherwise 
would ; thus adding about six minutes, on an average, to the 
length of each day. 

The atmosphere is said to be so dense about the North Pole as to bring the Sun above 
the horizon some days before he should appear, according to calculation. In 1596, some 
Dutch navigators, who wintered at NovaZembla, in latitude 76°, found that the Sun began 
to be visible 17 days before it should have appeared by calculation ; and Kepler computes 
that the atmospheric refraction must have amounted to 5°, or 10 times as much as with us. 

649. The twilight of morning and evening is produced partly 
by refraction, but maiuly by reflection. In the morning, when 
the Sun arrives within 18° of the horizon, his rays pass over 
our heads into the higher region of the atmosphere, -and are 
thence reflected down to the Earth. The day is then said to 
be dawn, and the light gradually increases till sunrise. In the 
evening, this process is reversed, and the twilight lingers till the 
Sun is 18° below the horizon. There is thus more than an hour 
of twilight both morning and evening. 

In the arctic regions, the Sun is never more than 18° below the horizon ; so that the 
twilight continues during the whole night. 

650. In making astronomical observations, for the purposes 
of navigation, &c, allowance has to be made for refraction, 
according to the altitude of the object, and the state of the 
atmosphere. Eor this purpose tables are constructed, showing 
the amount of refraction for every degree of altitude, from the 
horizon to the zenith. 



647. Amount of displacement of celestial objects by refraction? What follows? 
64S. Influence of refraction on length of days ? How about the North Pole ? 649. Cause 
of twilight? 650. What allowance for refraction ? Tables? 



302 ASTRONOMY. 

CHAPTER XYII. 

AURORA BOREALIS AND PARALLAX. 

651. The sublime and beautiful phenomena presented by the 
Aurora Borealis, or northern lights, as they are called, have been 
in all ages a source of admiration and wonder alike to the pea- 
sant and the philosopher. In the regions of the north (and 
indeed in many other places) they are regarded by the ignorant 
with superstitious dread, as harbingers of evil ; while all agree 
in placing them among the unexplained wonders of nature. 

These lights, or meteoric coruscations, are more brilliant in the arctic regions, appear- 
ing mostly in the winter season and in frosty weather. They commonly appear at twi- 
light near the horizon, and sometimes continue in that state for several hours without 
any sensible motion ; after which they send forth streams of stronger light, shooting 
with great velocity up to the zenith, emulating, not unfrequently, the lightning in vivid- 
ness, and the rainbow in coloring ; and again, silently rising in a compact majestic arch 
of steady white light, apparently durable and immovable, and yet so evanescent, that 
while the beholder looks upon it, it is gone. 

At other times they cover the whole hemisphere with their flickering and fantastic 
coruscations. On these occasions their motions are amazingly quick, and they astonish 
the spectator with rapid changes of form. They break out in places where none were 
seen before, skimming briskly along the heavens ; then they are suddenly extinguished, 
leaving behind an uniform dusky track, which, again, is brilliantly illuminated in the same 
manner, and as suddenly left a dull blank. Some nights they assume the appearance of 
vast columns ; exhibiting on one side tints of the deepest yellow, and on the other, 
melting away until they become undistinguishable from the surrounding sky. They 
have generally a strong tremulous motion from end to end, which continues till the whole 
vanishes. 

652. Maujpertius relates, that in Lapland, " the sky was 
sometimes tinged with so deep a red that the constellation Orion 
looked as though it were dipped in blood, and that the people 
fancied they saw armies engaged, fiery chariots, and a thousand 
prodigies." Gmelin relates, that, "in Siberia, on the confines 
of the icy sea, the spectral forms appear like rushing armies ; 
and that the hissing, crackling noises of those aerial fireworks 
so terrify the dogs and the hunters, that they fall prostrate on 
the ground, and will not move while the raging host is passing." 

Kerguelen describes " the night between Iceland and the Ferro 
Islands, as brilliant as the day" — the heavens being on fire with 
flames of red and white light, changing to columns and arches, 
and at length confounded in a brilliant chaos of cones, pyramids, 
radii, sheaves, arrows, and globes of fire. 

653. But the evidence of Captain Parry is of more value 

651. What said of the Aurora Borealis? How regarded by the ignorant? Where 
most brilliant? In what weather? Describe? 652. Observations of MauperUus, 
(hneUn y and Kerguelen ? 653. Observations of Oapt. Parry t 



AURORA BOREALIS AND PARALLAX. 303 

than that of the earlier travelers, as he examined the phenomena 
under the most favorable circumstances, during a period of 
twenty-seven consecutive months, and because his observations 
are uninfluenced by imagination. He speaks of the shifting 
figures, the spires and pyramids, the majestic arches, and the 
sparkling bands and stars which appeared within the arctic cir- 
cle, as surpassing his powers of description. They are, indeed, 
sufficient to enlist the superstitious feelings of any people not 
fortified by religion and philosophy. 

654. The colors of the polar lights' are of various tints. The 
rays or learns are steel grey, yellowish grey, pea green, celandine 
green, gold yellow, violet blue, purple, sometimes rose red, crim- 
son red, blood red, greenish red, orange red, and lake red. The 
arches are sometimes nearly black, passing into violet blue, grey, 
gold yellow, or white bounded by an edge of yellow. The luster 
of these lights varies in kind as well as intensity. Sometimes it 
is pearly, sometimes imperfectly vitreous, sometimes metallic. 
Its degree of intensity varies from a very faint radiance to a 
light nearly equaling that of the Moon. 

655. Many theories have been proposed to account for this 
wonderful phenomenon, but there seems to be none which is 
entirely satisfactory. One of the first conjectures on record 
attributes it to inflammable vapors ascending from the Earth 
into the polar atmosphere, and there ignited by electricity. Dr. 
Halley objects to this hypothesis, that the cause is inadequate 
to produce the effect. He was of opinion that the poles of the 
Earth were in some way connected with the aurora ; that the 
Earth was hollow, having within it a magnetic sphere, and that 
the magnetic effluvia, in passing from the north to the south, 
might become visible in the northern hemisphere. 

656. That the aurora borealis is, to some extent, a magnetical 
phenomenon, is thought, even by others, to be pretty clearly 
established by the following considerations : 

(1.) It has been observed, that when the aurora appears near 
the northern horizon in the form of an arch, the middle of it is 
not in the direction of the true north, but in that of the mag- 
netic needle at the place of observation ; and that when the 
arch rises towards the zenith, it constantly crosses the heavens 
at right angles, not to the true magnetic meridian. 

654. What said of the colors, &c, of these polar lights ? 655. Is there a satisfactory- 
explanation of these phenomena? What conjecture? Dr. Halley's objection? His own 
singular opinion ? 656. What evidences that the Aurora Borealis is of magnetic 
origin ? 



304 ASTRONOMY. 

(2.) When the beams of the aurora shoot up so as to pass 
the zenith, which is sometimes the case, the point of their con- 
vergence is in the direction of the prolongation of the dipping- 
needle at the place of observation. 

(3.) It has also been observed, that during the appearance of 
an active and brilliant aurora, the magnetic needle often becomes 
restless, varies sometimes several degrees, and does not resume 
its former position until after several hours. 

From these facts, it has been generally inferred that the aurora is in some way con- 
nected with the magnetism of the Earth ; and that the simultaneous appearance of the 
meteor, and the disturbance of the needle, are either related as cause and effect, or as 
the common result of some more general and unknown cause. 

65 T. Dr. Young, in his lectures, is very certain that the phe- 
nomenon in question is intimately connected with electro-mag- 
netism, and ascribes the light of the aurora to the illuminated 
agency of electricity upon the magnetical substance. 

It may be remarked, in support of the electro-magnetic theory, that in magnetism, the 
agency of electricity is now clearly established, and it can hardly be doubted that the 
phenomena both of electricity and magnetism are produced by one and the same cause ; 
inasmuch as magnetism may be induced by electricity, and the electric spark has been 
drawn from the magnet. 

658. Sir John Herschel also attributes the appearance of the 
aurora to the agency of electricity. This wonderful agency, says 
he, which we see in intense activity in lightning, and in a feebler 
and more diffused form traversing the upper regions of the 
atmosphere in the northern lights, is present, probably, in 
immense abundance in every form of matter which surrounds us, 
but becomes sensible, only when disturbed by excitements of 
peculiar kinds. 

PARALLAX OF THE HEAVENLY BODIES. 

659. Parallax is the difference between the altitude of any 
celestial object seen from the Earth's surface, and the altitude 
of the same object seen at the same time from the Earth's cen- 
ter ; or it is the angle under which the semi-diameter of the 
Earth would appear, as seen from the object. 

The true place of a celestial body is that point of the heavens 
in which it would be seen by an eye placed at the center of the 
Earth. The apparent place is that point of the heavens where 
the body is seen from the surface of the Earth. The parallax 

657 Dr. Young's opinion ? What remark in support of his views? 65S. Sir John 
Herschel's opinion? 659. Parallax? True place of a celestial body? Apparent? 
When parallax greatest? Least? Called what, and why ? What objects the greatest 
parallax ? 




AURORA BOREALIS AND PARALLAX. 305 

of a heavenly body is greatest when in the horizon, and is 
thence called the horizontal parallax. Parallax decreases as the 
body ascends towards the zenith, at which place it is nothing. 

The adjoining cut will afford a sufficient illustration. 
When the observer, standing upon the Earth at A, parallax of the planets. 

views the object at B, it appears to be at C, when, at 
the same time, if viewed from the center of the Earth, 
it would appear to be at D. The parallax is the angle 
B C D or A B E, which is the difference between the 
altitude of the object B, when seen from the Eanh's 
surface, and when seen from her center. It is also 
the angle under which the semi-diameter of the Earth, 
A E, is seen from the object B. 

As the object advances from the horizon to the 
zenith, the parallax is seen gradually to diminish, till 
at F it has no parallax, or its apparent and true place 
are the same. 

This diagram will also show why objects nearest 
the Earth have the greatest parallax, and those most 
distant the least; why the Moon, the nearest of all 
the heavenly bodies, has the greatest parallax ; while 
the fixed stars, from their immense distance, have no 
appreciable horizontal parallax — the semi-diameter 
of the Earth, at such a distance, being no more than a point. 

660. As the effect of parallax on a heavenly body is to depress 
it below its true place, it must necessarily affect its right ascen- 
sion and declination, its latitude and longitude. On this account, 
the parallax of the Sun and Moon must be added to their 
apparent altitude, in order to obtain their true altitude. 

The true altitude of the Sun and Moon, except when in the zenith, is always affected, 
more or less, both by parallax and refraction, but always in a contrary manner. Hence 
the mariner, in finding the latitude at sea, always adds the parallax, and subtracts the 
refraction, to and from the Sun's observed altitude, in order to obtain the true altitude, 
and thence the latitude. 

661. The principles of parallax are of great importance to 
astronomy, as they enable us to determine the distances of the 
heavenly bodies from the Earth, the magnitudes of the planets 
and the dimensions of their orbits. 

The Sun's horizontal parallax being accurately known, the 
Earth's distance from the Sun becomes known ; and the Earth's 
distance from the Sun being known, that of all the planets may 
be known also, because we know the exact periods of their 
sidereal revolutions, and, according to the third law of Kepler, 
the squares of the times of their revolutions are proportional to 
the cubes of their mean distances. Hence, the first great 
desideratum in astronomy, where measure and magnitude are 
concerned, is the determination of the true parallax. 

At a council of astronomers assembled in London some years since, from the mrjt 

660. Effect of parallax? How obtain true altitude? How differ from refraction? 
How then obtain true altitude ? 661. Use of parallax ? How employed ? No',e ? 



306 



ASTRONOMY. 



learned nations in Enrope, the Sun's mean horizontal parallax was settled, as tie result 
of their united observations, at 0° 0' 8".5776. Now the value of radius, expressed like- 
wise in seconds, is 206264".8; and this divided by 8'.5776, gives 24047 for the distance of 
the Sun from the the Earth, in semi-diameters of the latter. If we take the equatorial 
semi-diameter of the Earth, as sanctioned by the same tribunal, at e7924-s-2=) 3962 miles, 
we shall have 24047x3962=95,273,869 miles for the Sun's true distance. 

A TABLE OF THE SUN'S PARALLAX IN ALTITUDE. 



Sun's 
Altit. 


Sun's Horizontal Parallax. 


Sim's 
Altit. 


Sun's Horizontal Parallax. 




8.4 


8.5 


8.6 


8.7 


8.8 


45 


8.4 


8.5 


8.6 


8.7 


8.8 





8.40 


8.50 


8.60 


8.70 


8.80 


5.94 


6.01 


6.08 


6.15 


6.22 


5 


8.37 


8.47 


8.57 


8.67 


8 77 


50 


5.40 


5.46 


5.53 


5.59 


5.66 


10 


8.27 


8.37 


8.47 


8.57 


8.67 


55 


4.82 


4.83 


4.93 


4.99 


5.05 


15 


8.11 


8.21 


8.31 


8.40 


8.50 


60 


4.20 


4.25 


4.30 


4.35 


4.40 


20 


7.89 


7.99 


8.08 


8.18 


8.27 


65 


3.55 


3.59 


3.63 


3.68 


3.72 


25 


7.61 


7.70 


7.79 


7.88 


7.98 


70 


2.87 


2.91 


2.94 


2.98 


3.01 


30 


7.28 


7.36 


7.45 


7.53 


7.62 


i 75 


2.17 


2.20 


2.23 


2.25 


2.28 


35 


• 6.88 


6.96 


7.04 


7.13 


7.21 


: so 


1.46 


1.48 


1.49 


1.51 


1.53 


40 


6.44 


6.51 


6.59 


6.66 


6.74 


85 


0.73 


0.74 


0.75 


0.76 


0.77 


45 


5.94 


6.01 


6.08 6.15 


6.22 


90 


0.00 


0.00 


0.00 


0.00 


0.00 



662. The change in the apparent position of the fixed stars, 
caused by the change of the Earth's place in her revolution 
around the Sun, is called their annual parallax. So immense 
is their distance, that the semi-annual variation of 190,000,000 
of miles in the Earth's distance, from all those stars that lie in 
the plane of her orbit, makes no perceptible difference in their 
apparent magnitude or brightness. 

The following cut will illustrate our meaning: 



D.- """" 3*4. ~~*NC A 

■fr\ %$? ;;**- " * 

B 

Let A represent a fixed star in the plane of the Earth's orbit, B. At C, the Earth is 
190,000,000 of miles nearer the star than it will be at D six months afterward ; and yet 
this semi-annual variation of 190,000,000 miles in the distance of the star is so small a 
fraction of the whole distance to it, as neither to increase or diminish its apparent 
brightness. 

663. It is only those stars that are situated near the axis of 
the Earth's orbit whose parallax can be measured at all, on 



662. What meant by Earth's annual parallax ? Effect of variation of Earth's dis- 
tance on the fixed stars? Diagram. 663. What stars have perceptible parallax? 



AURORA BOREALIS AND PARALLAX. 307 



PARALLAX OF THE STARS. 



\ i 


/ E 


B*' 




A 

I 


V 


/ 


\ 


/ 

D ^- 


\ 
-_ \ 

—- --"'a 



account of its almost imperceptible quantity. 
So distant are they, that the variation of 
190,000,000 miles in the Earth's place 
causes an apparent change of less than 1' in 
the nearest and most favorably situated 
fixed star. 

Let A represent the Earth on the 1st of January, and B a 
star observed at that time. Of course, its apparent place in 
the more distant heavens will be at C. But in six months the 
Earth will be at D, and the star B will appear to be at E. 
The angle A B D or C B E will constitute the parallactic angle. 
In the cut, this angle amounts to about 4S°, whereas the real 
parallax of the stars is less than -jr^-th of one degree, or 
__J _th part of this amount. Lines approaching each other 
thus slowly would appear parallel ; and the Earth's orbit, if 
filled with a globe of fire, and viewed from the fixed stars, 
would appear but a point of light 1' in diameter ! For a 
splendid diagram illustrative of the annual parallax of the stars, see Map I., of the Atla3. 

ABERRATION OP LIGHT. 

664. In the year 1725, Mr. Molyneux and Dr. Bradley fixed 
up a very accurate and costly instrument, in order to discover 
whether the fixed stars had any sensible parallax, while the Earth 
moved from one extremity of its orbit to the other ; or which 
is the same, to determine whether the nearest fixed stars are 
situated at such an immense distance from the Earth, that any 
star which is seen this night, directly north of us, will, six 
months hence, when we shall have gone 190,000,000 of miles to 
the eastward of the place we are now in, be then seen exactly 
north of us still, without changing its position so much, as the 
thickness of a spider's web. 

665. These observations were subsequently repeated, with but 
little intermission, for twenty years, by the most acute observers 
in Europe, and with telescopes varying from 12 feet to 36 feet 
in length. In the mean time, Dr. Bradley had the honor of 
announcing to the world the very nice discovery made while 
endeavoring to ascertain the parallax of the fixed stars, that 
the motion of light, combined with the progressive motion of the 
Earth in its orbit, causes the heavenly bodies to be seen in a differ- 
ent position from what they would be, if the eye were at. rest. Thus 
was established the principle of the Aberration of Light. 

666. This principle, or law, now that it is ascertained, seems 

Amount? Diagram, and explanation. 664. What experiment by Molyneux ana 

Bradley? With what results ? 665. What further observations for the same purpose? 
What discovery made while investigating the subject of parallax ? What is the aberra- 
tion of light ? 666. What remarks upon the principle or law of observation ? How is 



308 ASTRONOMY. 

not only very plain, but self-evident. For if light be progres- 
sive, the position of the telescope, in order to receive the ray, 
must be different from what it would have been if light had 
been instantaneous, or if the Earth stood still. Hence the place 
to which the telescope is directed will be different from the true 
place of the object. 

The quantity of this aberration is determined by a simple 
proposition. The Earth describes 59' 8" of her orbit in a day 
= 3548", and a ray of light comes from the Sun to us in 8' 13" 
=493" : now 24 hours or 86400" : 493 : : 3548: 22"; which 
is the change in the star's place, arising from the cause above- 
mentioned. 



CHAPTER XVIII. 



PEACTIOAL ASTEONOMY— EEFLECTION AND EEFEAC- 
TION OF LIGHT. 

66 T. Practical Astronomy has respect to the means employed 
for the acquisition of astronomical knowledge. It includes the 
properties of light, the structure and use of instruments, and 
the processes of mathematical calculation. 

In the present treatise, nothing further will be attempted than a mere introduction to 
practical astronomy. In a work designed for popular use, mathematical demonstrations 
would be out of place. Still, every student in astronomy should know how telescopes are 
made, upon what laws they depend for their power, and how they are used. It is for this 
purpose mainly that we add the following chapters on practical astronomy. 

PROPERTIES OF LIGHT. 

668. Light is that invisible ethereal substance by which we 
are apprised of the existence, forms, and colors of material 
objects, through the medium of the visual organs. To this sub- 
tile fluid we are especially indebted for our knowledge of those 
distant worlds that are the principal subjects of astronomical 
inquiry. 

669. The term light is used in two different senses. It may 
signify either light itself, or the degree of light by which we are 
enabled to see objects distinctly. In this last sense, we put light 



the quantity of aberration determined? 667. Subject of Chapter XVIH. ? What is 
practical astronomy ? How far discussed in this treatise? 66S. Define light. For 
what indebted to it? 669. Different senses in which the term is used? What is 



REFLECTION AND REFRACTION OF LIGHT. 309 

in opposition to darkness. But it should be borne in mind, that 
darkness is merely the absence of that degree of light which is 
necessary to human vision ; and when it is dark to us, it may be 
light to many of the lower animals. Indeed, there is more or 
less light, even in the darkest night, and in the deepest dungeon. 

" Those unfortunate individuals," says Dr. Dick, " who have been confined in the dark- 
est dungeons, have declared, that though, on their first entrance, no object could be per- 
ceived, perhaps for a day or two, yet, in the course of time, as the pupils of their eyes 
expanded, they could readily perceive rats, mice, and other animals that infested their 
cells, and likewise the walls of their apartments ; which shows that, even in such situa- 
tions, light is present, and produces a certain degree of influence." 

610. Of the nature of the substance we call light, two theo- 
ries have been advanced. The first is, that the whole sphere of 
the universe is filled with a subtile fluid, which receives from 
luminous bodies an agitation ; so that, by its continued vibra- 
tory motion, we are enabled to perceive luminous bodies. This 
was the opinion of Descartes, Euler, Huygens, and Franklin. 

The second theory is, that light consists of particles thrown 
off from luminous bodies, and actually proceeding through space. 
This is the doctrine of Newton, and of the British philosophers 
generally. 

Without attempting to decide, in this place, upon the relative merits of these two hypo- 
theses, we shall use those terms, for convenience sake, that indicate the actual passage 
of light from one body to another. 

611. Light proceeds from luminous bodies in straight lines, 
and in all directions. It will not wind its way through a crooked 
passage, like sound ; neither is it confined to a part of the cir- 
cumference around it. 

As the Sun may be seen from every point in the solar system, and far hence into space 
in every direction, even till he appears but a faint and glimmering star, it is evident that 
he fills every part of this vast space with his beams. And the same might be said of 
every, star in the firmament. 

612. As vision depends not upon the existence of light merely, 
but requires a certain degree of light to emanate from the object, 
and to enter the pupil of the eye, it is obvious that if we can, 
by any means, concentrate the light, so that more may enter the 
eye, it will improve our perception of visible objects, and even 
enable us to see objects otherwise wholly invisible. 

Some animals have the power of adapting their eyes to the existing degree of light. 
The cat, horse, &c, can see day or night ; while the owl, that sees well in the night, sees 
poorly in the day-time. 

613. Light may be turned out of its course either by reflection 

darkness ? Can it be dark and light at the same time ? Is there any place without 
light? Quotation from Dr. Dick ? 670. What theories of the nature of light, and by 
whom supported respectively? Remark of author? 6T1. How light proceeds from 
luminous bodies? Radiations from Sun and stars? 672. How improve vision, and 
why ? Animals ? 673. How is light turned out of its course ? 



310 



ASTRONOMY. 



or refraction. It is reflected when it falls upon the highly polished 
surface of metals and other intransparent substances ; and 
refracted when it passes through transparent substances of diffe- 
rent densities, as already illustrated in Chapter XYI. 



REFRACTION BY GLASS LENSES. 



614. A lensis a piece of glass, or other transparent substance, 
of such a form as to collect or disperse the rays of light that 
are passed through it, by refracting them out of a direct course. 
They are of different forms, and have different powers. 



In the adjoining cut, we have an edgewise 
view of six different lenses. 

A is the plano-convex, or half a double con- 
vex lens ; one side being convex and the other 
plane. 

B is a plano-concave ; one surface being con- 
cave, and the other plane.' 

C is a double-convex lens, or one that is 
bounded by two convex surfaces. 

D is a double-concave lens, or a circular piece 
of glass hollowed out on both sides. 

E is a concavo-convex lens, whose curves 
differ, but do not meet, if produced. 

F is a meniscus, or a concavo-convex lens, 
the curves of whose surfaces meet. 



LENSES OF DIFFERENT FORMS. 




615. A double-convex lens 
converges parallel rays to a 
point called the focus ; and 
the distance of the focus 
depends upon the degree of 
convbxity. 

In the first of these cuts, the lens is 
quite thick, and the focus of the rays is 
quite near ; but the other being less 
convex, the focus is more distant. 

616. The distance of the 
focus of a double-convex glass 
lens is the radius of the sphere 
of its convexity. 

In this cut, it will be seen that the 
parallel rays A are refracted to a focus 
at C, by the double-convex lens B, the 
convexity of whose surfaces is just equal 
to the curve of the circle D. 

611. The focal distance of 
a plano-convex lens is equal to 
the diameter of the sphere 
formed by the convex surface produced. 



LIGHT REFRACTED BY LENSES. 




DOUBLE CONVEX — FOCAL DISTANCE. 




674. What is a lens? Draw and describe different kinds. 675. Refracting power of 
double-convex lens ? Focal distance ? Diagram, and illustrate. 676. How focal dis- 
tance governed ? Diagram, and illustrate. 677. What is the focal distance of a 



REFLECTION AND REFRACTION OF LIGHT. 



311 



It must be borne in mind, that plano-concave — focal distance. 

light is refracted both when it 
enters, and when it leaves a double 
convex lens, and in both instances 
In the same direction ; and, so far 
as the distance of the focus is 
concerned, to the same extent. 
But when the lens is convex only 
on one side, half its refracting 
power is gone, so that the rays 
are not so soon refracted to a 
focus. In this case, the focal dis- 
tance is equal to the diameter of 
the sphere formed by extending 
the convex surface of the lens; 
while with the double-convex lens, 
the focal distance is only equal to 

the radius of such sphere. In the cut, the parallel rays A are refracted to a focus at 
B, by the plano-concave lens C ; and the distance C B is the diameter of the circle 
D, formed by the convex surface of the lens C produced. 

6*18. A double-con- 




RAYS DISPERSED BY REFRACTION. 




cave lens disperses pa- 
rallel rays, as if they 
diverged from the cen- 
ter of a circle formed 
by the convex surface 
luced. 



prodi 

In this cut, the parallel rays 
A are dispersed by the double- 
concave lens C, as shown at 
B ; and their direction, as 
thus refracted, is the same 

as if they proceeded from the point D, which is the center of a circle formed by the 
concave surface of the lens produced. 

6T9. Common spectacles, opera-glasses, burning-glasses, and 
refracting telescopes are made by converging light to a focus, by 
the use of double-convex lenses. 

BURNING-GLASS. 

The ordinary burning-glass, which may be 
bought for a few shillings, is a double-convex 
disk of glass two or three inches in diameter, 
inclosed in a slight metallic frame, with a han- 
dle on one side. Old tobacco-smokers some- 
times carry them in their pockets, to light then- 
pipes with when the Sun shines. In other in- 
stances, they have been so placed, as to fire a 
cannon in clear weather, by igniting the prim- 
ing at 12 o'clock. 

The adjoining cut represents a large burn- 
ing-glass converging the rays of the Sun to a 
focus, and setting combustible substances on 
fire. Such glasses have been made powerful 
enough to melt the most refractory substances, 
as platinum, agate, <fec. " A len3 three feet in 
diameter," says Professor Gray, " has been 
known to melt cornelian in 75 seconds, and a 
piece of white agate in 30 seconds." 

plano-convex lens ? Diagram. 678. Effect of double-convex lens ? Amount of diver- 
gency of rays ? 679. What articles made with double-convex lenses ? Uses ? Powe 
of burning glasses ? ' 




312 



ASTRONOMY. 



REFEECTION BY A PLANE MIRROR. 




REFLECTION BY A CONCAVE MIRROR. 



REFLECTION OF LIGHT. 

680. We have now shown how light may be turned out of its 
course, and analyzed, dispersed, or converged to a point by 
refraction. Let us now consider how it may be converged to a 
focus by reflection. 

When light falls upon a highly-polished surface, especially of 
metals, it is reflected or thrown off in 
a new direction, and the angles of 
contact and departure are always 
equal. 

Let A B represent the polished metallic surface, 
C the source of light, and the arrows the direction 
of the ray. Then D would represent the angle of 
incidence or contact, and E the angle of reflection 
or departure — which angles are seen to be equal. 

681. A concave mirror re- 
flects parallel rays back to a 
focus, the distance of which 
is equal to half the radius of 
the sphere formed by the 
concave surface produced. 

In this cut, the parallel rays A fail 
upon the concave mirror B B, and are 
reflected to the focus C, which is half 
the radius of the sphere formed by the 
surface of the mirror produced. If, 
therefore, it was desirable to construct 
a concave mirror, having its focus 10 
feet distant, it would only be necessary 
to grind it on the circle of a sphere 
having a radius of 20 feet. 

682. In reflection, a por- 
tion of the light is absorbed 
or otherwise lost, so that a 
reflector of a given diameter 
will not converge as much light to a focus as a double-convex 
lens of the same size. In the latter case all the light is trans- 
mitted. Still, reflectors have been found of such power as to 
melt iron, and other more difficult substances. 

We have now considered so much of optics as is necessary to an understanding of the 
principles upon which telescopes are constructed; and, for further particulars, shall 
refer the student to books on Natural Philosophy. 




680. What now shown in this chapter? What next? What is reflection, and when 
does it take place? What law governs it? Diagram. 681. How does a concave 
mirror reflect parallel rays ! Distance of focus ? Diagram. How would you construct 
a concave mirror with a 10 feet focus ? 682. Is all the light falling upon a polished 
surface reflected ? What then ? Closing note ? 



TELESCOPES REFRACTORS AND REFLECTORS. 313 

CHAPTER XIX. 

TELESCOPES— BEFKACTOKS AND KEFLECTORS. 

683. A telescope is an optical instrument employed in view- 
ing distant objects, especially the heavenly bodies. The term 
telescope is derived from two Greek words, viz., tele, at a distance, 
and skopeo, to see. So far as is now known, the ancients had no 
knowledge of the telescope. Its invention, which occurred in 
1609, is usually attributed to Galileo, a philosopher of Florence, 
in Italy. 

The discovery of the principle upon which the refracting telescope is constructed was 
purely accidental. The children of one Janaen, a spectacle-maker of Middleburgh, in 
Holland, being at play in their father's shop, happened to plac-e two glasses in such a 
manner, that in looking through them, at the weathercock of the church, it appeared to 
be nearer, and much larger than usual. This led their father to fix the glasses upon a 
board, that they might be ready for observation ; and the news of the discovery was soon 
conveyed to the learned throughout Europe. Galileo hearing of the phenomenon, soon 
discovered the secret, and put the glasses in a tube, instead of on a board ; and thus the 
first telescope was constructed. 

684. The telescope of Galileo was but one inch in diameter, 
and magnified objects but 30 times. Yet with this simple 
instrument he discovered the face of the Moon to be full of ine- 
qualities, like mountains and valleys ; the spots on the Sun ; the 
phases of Yenus ; the satellites of Jupiter ; and thousands of 
new stars in all parts of the heavens. 

Notwithstanding this propitious commencement, so slow was the progress of the 
telescope towards its present state, that in 1816, Bonnycastle speaks of the 30-fold mag- 
nifying power of the telescope of Galileo as " nearly the greatest perfection that this 
kind of telescope is capable of!" 

685. If he be the real author of an invention who, from a 
knowledge of the cause upon which it depends, deduces it from 
one principle to another, till he arrives at the end proposed, 
then the whole merit of the- invention of the telescope belongs to 
Galileo. The telescope of Jansen was a rude instrument of mere 
curiosity, accidentally arranged ; but Galileo was the first who 
constructed it upon principles of science, and showed the practi- 
cal uses to which it might be applied. 

It is said that the original telescope constructed by Galileo is still preserved in the 
British Museum. A pigmy, indeed, in its way, but the honored progenitor of a race of 
giants ! 

686. The discovery of the telescope tended greatly to sustain 

6S3. Subject of Chapter XIX. ? Telescope? Derivation? Ancient or modern ? In- 
ventor? Incidents of discovery? 684. Galileo's telescope? Discoveries with it? 
Progress in telescope making? 685. Is Galileo entitled to the honor of inventing the 
telescope ? Where is his ? 6S6. Relation of discovery to Copernican theory ? Effects 



314 



ASTRONOMY. 



the Copernican theory, which had just been promulgated, and of 
which Galileo was an ardent disciple. Like Copernicus, how 
ever, his doctrines subjected him to severe persecutions, and he 
was obliged to renounce them. 

The following is his renunciation, made June 28,1633: " I, Galileo, in the seventieth 
year of my age, on bended knees before your eminences, having before my eyes and 
touching with my hands the Holy Gospels, I curse and detest the error of the Earth's 
movement." As he left the court, however, after this forced renunciation, he is said to 
have stamped upon the Earth, and exclaimed, " It does move, after all ?" Ten years 
after this, he was sent to prison for the same supposed error ; and soon, his age advanc- 
ing, the grave received him from the malice of his persecutors. 

DIFFERENT KINDS OF TELESCOPES. 

68T. Telescopes are of two kinds — Reflectors and Refractors. 
Refracting telescopes are made by refracting the light to a focus 
with a glass lens (6*75) ; and reflecting telescopes, by reflecting 
it to a focus with a concave mirror (681). Besides this 
general division, there are various kinds both of reflectors and 
refractors. 

Telescopes assist vision in various ways — first, by enlarging the visual angle under 
which a distant object is seen, and thus magnifying that object ; and, secondly, by 
converging to a point more light than could otherwise enter the eye — thus rendering 
objects distinct or visible that would otherwise be indistinct or invisible. 

All the light falling upon a six or a twelve inch lens may be converged to a focusj so 
as to be taken into the human eye through the pupil, which is but one-fourth of an inch 
in diameter. Our vision is thus made as perfect b^ art as if nature had given us ability 
to enlarge the eye till the pupil was a foot in diameter. 

688. Refracting telescopes may consist of a double-convex 
lens placed upon a stand, without tube or eye-piece. Indeed, a 
pair of ordinary spectacles is nothing less than a pair of small 
telescopes, for aiding impaired vision. 

REFRACTING TELESCOPE WITH A SINGLE LENS. 




Here the parallel rays are seen to pass through the lens at A, and to be so converged 
to a point as to enter the eye of the beholder at B. His eye is thus virtually enlarged to 
the size of the lens at A. But it would be very difficult to direct such a telescope toward 
celestial objects, or to get the eye in the focus after it was thus directed. 

upon Galileo? His renunciation? Death? 687. Kinds of telescopes? Describe. 
How assist vision ? Illustration. 688. Simplest form of refracting telescope ? 



TELESCOPES REFRACTORS AND REFLECTORS. 



315 



689. The Galilean telescope consists of two glasses — a doubie.- 
convez next the object, and a double-concave near the eye. The 
former converges the light till it can be received by a small 
double-concave, by which the convergency is corrected (502), 
and the rays rendered parallel again, though in so small a beam 
as to be capable of entering the eye. 



GALILEAN TELESCOPE. 




Here the light is converged by the lens A, till it can be received by the double-concave 
lens B, by which the rays are made to become a small parallel beam that can enter the 
eye at C. This was the form of the telescope constructed by Jansen, and improved by 
Galileo ; on which account it is called the Galilean telescope. In the cut, the two lenses 
are represented as fastened to a board, as first exhibited by Jansen. 

690. The common astronomical telescope consists of two 
glasses — viz., a large double-convex lens next the object, called 
the object-glass ; and a small double-convex lens or microscope 
next the eye, called the eye-piece. For the greater convenience in 
using, they are both placed in a tube of wood or metal, and 
mounted in various ways, according to their size, and the pur- 
poses to which they are devoted. 

LENSES PLACED IN A TUBE. 




A is the object-glass, B the eye-piece, and C the place where the tube, in which the eye- 
piece is set, slides in and out of the large tube, to adjust the eye-piece to the focal dis- 
tance. By placing the lenses in a tube, the eye is easily placed in the focus, and the 
object-glass directed toward any desired object. 

691. The object-glass of a telescope is usually protected, when 
not in use, by a brass cap that shuts over the end of the instru- 
ment ; and the eye-pieces, of which there are several, of differ- 



689. Galilean telescope ? Why called Galilean ? 690. How common astronomical 
telescopes made? Why in tube? 691. How object-glass protected? What said of 
eye-pieces ? 



B.G. 



14 



316 



ASTRONOMY. 



REFRA.CVING TELESCOPE MOUNTED ON A STAH». 




ent magnifying powers, 
are so fixed as to screw 
into a small movable tube 
in the lower end of the 
instrument, so as to adjust 
them respectively, to the 
focus, and to the eyes of 
different observers. Such 
telescopes usually repre- 
sent objects in an invert- 
ed position. 

The adjoining cut represents the 
simplest form of a mounted refrac- 
tor. The object-glass is at A, where 
the brass cap may be seen cover- 
ing it. B is the small tube into 
which the eye-piece is screwed, and 
which is moved in and out by the 
small screw C. Two eye-pieces 
may be seen at D — one short one, 
for astronomical observations, and 
a long one, for land objects. For 
viewing the Sun, it is necessary to 
add a screen, made of colored 
glass. At E, a bolt goes into a 
socket in the top of the stand, in 
which it turns, allowing the tele- 
scope to sweep around the horizon ; while the joint, connecting the saddle in which the 
telescope rests with the top of the bolt, allows it to be directed to any point between the 
horizon and the zenith. But such stands answer only for comparatively small instruments. 

692. Refracting telescopes are mounted in various ways. 
So important is it that they should not shake or vibrate, that, in 
most observatories, the stand rests upon heavy mason-work in 
no way connected with the building, so that neither the wind 
nor the tread of the observer can shake it. They are then fur- 
nished with a double axis, which allows of motion up and down, 
or east and west ; and two graduated circles show the precise 
amount of declination and right ascension. 

They are often furnished with clockwork, by which the telescope is made to move 
westward just as fast as the Earth turns eastward ; so that the celestial object being 
once found, by setting the instrument for its right ascension and declination, or by the 
aid of the Finder — a small telescope attached to the lower end of the large one — it may 
be kept in view by the clockwork for any desirable length of time. A telescope thus fur- 
nished with right ascension and declination circles is called an Equatorial, or is said to 
be equatorially mounted, because it sweeps east and west in the heavens parallel to the 
equator. 

693. The object-glasses of telescopes are not always made of 
a single piece of glass. They may be made of two concavo-con- 
vex glasses, like two watch crystals, with their concave sides 

692. How refractors mounted, and why? When equatorial, and why? 693. How 
object-glasses made ? What a lens ? A Barlow lens ? 



TELESCOPES REFRACTORS AND REFLECTORS. 



317 



towards each other, or with a thin double concave glass between 
them. They are thus double, or triple ; but when thus con- 
structed, the whole is called a lens, as if composed of a single 
piece. 

Lenses have also been formed by putting two concavo-convex glasses together, and 
filling the space between them with some transparent fluid. These are called Barlow 
lenses, from Prof. Barlow, their inventor. 

694. As a prism analyzes the light, and exhibits different 
colors, so a double convex lens may analyze the light that falls 
near its circumference, and thus represent the outside of the 
heavenly bodies as colored. But this defect is remedied by 
using discs made of different kinds of glass, so as to correct one 
refraction by another. Refracting telescopes thus corrected are 
called Achromatic telescopes. 

Achromatic is from the Greek a chroma, which signifies destitute of color. Most 
refracting telescopes are now so constructed as to be achromatic. 

695. It is but recently that any good refracting telescopes 
have been made in this country. The best have formerly been 
made in Germany and France ; but they are now manufactured 
with success, and to considerable extent, by Mr. Henry Fitz, 
Jun., New York City. The glass used by him is obtained from 
Paris, because none suitable for large telescopes has yet been 
made in America. His telescopes are perfectly achromatic, and 
are sold much cheaper than imported ones of the same size and 
value. 

Mr. Fitz has recently made a very valuable improvement in the mounting of telescopes 
— one which is not only much superior to the old method, but which costs only about 
one-half as much. This improvement consists in using a single piece of cast-iron in the 
place of several pieces of brass work. It is very simple, secures great steadiness to the 
instrument, and is easily adjusted. 

The writer is fully satisfied of the value of this improvement, and would recommend it, 
as well as Mr. Fitz's instruments, to all institutions and amateur astronomers about to 
purchase either. Besides patronizing a worthy American optician, they will get as good 
a telescope and much better mounting than by sending abroad, and at far less expense 
The following is a list of telescopes manufactured by Mr. Fitz, with the prices attached : 

PRICES OF FITZ*S TELESCOPES, EQTJATORULLY MOUNTKD, ETC. 



Focal Length. 


Object Glass. 


New Style 
Mounting. 


Old Style 
Mounting. 


Difference of Coat. 


9 ft. 


8% inches. 


$1,400 


$2,300 


$900 


11 " 


8% " 




2,220 




10 " 8 inch. 


8 


1,500 


2,000 


850 


8 " 


6% " 


700 


1,200 


500 


7 " 


5 " 


400 


750 


350 


7 " 


m " 


800 


500 


200 


5 " 


I 4 


225 


400 


175 



694. What is an Achromatic telescope? Derivation of term ? 695. Where telescopes 
formerly made ? Where and by whom now, in this country ? Where is the glass ob- 
tained ? What said of Mr. Fitz's telescopes ? 



318 



ASTRONOMY. 



A FITZ REFRACTOR. 



He will furnish a very good telescope of three inches aperture for $120, equatorially 
mounted, with eye-pieces, &c. The size priced at $225, is equal to that at Yale College. 
A good revolving dome for an observatory building can be built for $100. 

This note is inserted exclusively for the benefit of institutions using the work, and 
without any request or remuneration from Mr. Fitz. Orders or letters of inquiry may be 
addressed to Henry Fitz, Jun., 23T Third-street, New York. 

696. The adjoining cut represents an 
equatorial telescope manufactured by Mr. 
Henry Fitz of New York — the one used 
by the author in making most of his obser- 
vations. Its object-glass is six inches in 
diameter, and its focal length eight feet. 
It is perfectly achromatic, and performs all 
the tests laid down in Dick's Practical 
Astronomer, as evidence of a good instru- 
ment, with perfect ease. Under favora- 
ble circumstances, it shows the sixth star 
in the trapezium of Orion, and to show 
Polaris double is a very easy test indeed. 

A is the declination circle, and B the circle of right 
ascension. The two sticks hanging from these circles are 
used to move the instrument in right ascension or decli- 
nation, while the observer is at the eye-piece. 

The Finder is seen attached to the lower end of 
the large instrument. It takes in a larger field of 
view in the heavens than the latter, and enables 
the observer to look up objects with facility, and 
bring them into the field of the larger instrument. 

This instrument has no clockwork attached. It 
rests upon a pillar of heavy masonwork, the top of 
which may be seen in the cut; and in the hands of 
its present owner, Lewis M. Rutherford, Esq., has 
already rendered very efficient service. 

697. The adjoining cut represents 
one of the largest telescopes in the 
United States. It is located in the 
observatory on Mount Adams, near 
Cincinnati, Ohio, and was for a time 
under the direction of Prof. Mitchel, by 
whose instrumentality it was purchased 
and mounted. 

The object-glass is about 12 inches in diameter, 
with a focal distance of IT feet. It was purchased 
in Munich, Germany, in 1844, at an expense of 
nearly ten thousand dollars. Ti ere is but one 
larger than this in the United States, and but two 
larger in the world. 




REFRACTING TELESCOPE AT CINCIN- 
NATI, OHIO. 




696. Mr. Rutherford's Telescope ? By whom made ? 667. Cincinnati refractor— 
where located? By whom purchased? Where? When? Cost? Size and focal dis« 
tance ? Comparative size ? 



DIFFERENT KINDS OF TELESCOPES. 



319 



THE GREAT CRAIG TELESCOPE, WANDSWORTH COMMON, NEAR LONDON. 




698. This is the largest refracting telescope ever constructed 
The object-glass is two feet in diameter, with a focal distance of 
16 feet. The tube is of heavy sheet iron, and shaped somewhat 
like a cigar. It is 13 feet in circumference in the largest place, 
and weighs about three tons. 

This telescope is suspended from a brick tower, 65 feet high, 15 feet in diameter, and 
weighing 220 tons. The top of the tower, from which the telescope is suspended, re- 
volves ; and by a chain running over pulleys, and a weight and windlass, it is balanced, 
and raised or lowered. The lower end rests on a small carriage, that runs upon a circu- 
lar railroad around the tower, at the distance of 52 feet from its center. By these means 
it is directed to almost any point in the heavens. It is called the " Craig" telescope, in 
honor of the Rev. Mr. Craig, under whose direction, and at whose expense, it was con- 
structed. It is located at Wandsworth Common, near London. 



698. Describe the Craig telescope. Object glass? Focal distance? Tube? How 
mounted? Why called " Craig" telescope ? Where located ? 



320 



ASTRONOMY. 



699. Besides this monster refractor, there are several other 
very fine instruments in Europe ; as the Dorpat telescope, Sir 
James South's, the Northumberland refractor, the Oxford tele- 
scope, &c. Several colleges and seminaries in the United States 
have observatories connected with them, and telescopes of great- 
er or less value. The largest is at Cambridge, near Boston. 



PUBLIC OBSERVATORIES AND TELESCOPES IN THE UNITED STATES. 



Observatories. 



Yale College 

Wesleyan University. . 

Williams College 

Hudson, Ohio 

Philadelphia 

West Point 

Washington 

Cincinnati 

Cambridge 

Dartmouth College 

Georgetown " 

Erskine " 

Shelby " .... 
Columbia (S. C.) College 
Columbia (Mo.) 



When 
procured. 



1830 
1S36 
1S36 
1852 
1S37 
1840 
1841 
1844 

1846 
1848 
1849 

1850 
1851 
1852 



THEIR TELESCOPES. 



Name of 
maker. 



Dollond. 

Lerebours. 

Holcomb. 

A. Clark. 

Simms. 

Merz. 

Lerebours. 

Merz. 



Simms. 

Fitz. 

Merz. 

Fitz. 



Focal 
length. 



ft. in. 

10 — 

7 — 

10 — 



15 3 

17 — 

22 6 

9 — 

7 6 

7 — 
10 4 

8 4 
5 — 



Aperture 
object-gl; 



inches. 
5 
6 
reflector. 
7 
4 



9-6 

12 

15 
6-4 
4-8 
5-6 

'7-5 
6% 
4 



$1,000 
1,000 



6,000 
9,437 

19,S42 

1,600 
1,050 
8,500 
1,200 
225 



100. Quite a number of very respectable private observato- 
ries are also in operation in different parts of the country. The 
following table includes most of them : 



PR1VATK OBSERVATORIES. 





TELESCOPES. 


Owner and Location. 


When 
Procured. 


Maker. 


Focal 

length. 


Object-glass. 


Cost. 


J. Jackson, near Philadelphia 

Mr. Longstreet, Philadelphia 

S. G-. Gummere, Burlington, N. J. 

R. Vanarsdale, Newark, N. J 

W. S. Van Duzee, Buffalo, N. Y... . 

W. S. Dickie, Elkton, Ky 

D. Mosman, Bangor, Me 

J. Campbell, New York 


1846 

1847 
', 1S50 
« 1551 

(i 
1852 


Fitz. 

(i 

u 
(< 

u 


ft. in. 
8 4 
7 — 

5 — 

7 — 

8 4 
11 — 

6 — 
5 — 

10 — 


inches. 
6 3-10 
5 
4 
5 

6% 
8% 

4 

8 


$1 ,833 

900 

425 

750 

1,000 

2,220 

300 

225 

1,150 













699. What other refractors in Europe besides the Craig? Public observatories in this 
country? Largest telescope? Table? 700. Private observatories — names? Tele- 
scopes — by whom mostly made ? What other table ? 



DIFFERENT KINDS OF TELESCOPES. 



321 



The following is a list of the principal foreign observatories, with their latitude and 
longitude. The longitude is from Greenwich, near London. 



FOREIGN OBSERVATORIES- — THEIR LATITUDE AND LONGITUDE. 



Altona 

Armagh 

Berlin 

Brussels 

Cambridge 

Cape of Good Hope. 

Copenhagen 

Dorpat.. 

Lublin 

Edinburgh , 

Gottingen 

Greenwich 

Konigsberg 

Munich 

Palermo 

Paris -. ... 

Petersburg 

Koine 

Turin 

Vienna 



53 32 45 

54 21 12.7 



52 30 16.7 N. 
50 51 10.7 N. 
52 12 51.8 N. 



55 40 

58 22 

53 23 

55 57 

51 31 

51 28 



48 50 

59 56 

41 53 

45 4 

48 12 



53 N. 

47.1 N. 
13 N. 

23.2 N. 
47.9 N. 
3S.2 N. 

50.4 N. 
45 N. 
44 N. 
13 N. 
29.7 N. 

54 N. 
6 N. 

35.5 N. 



Longitude in Time. 



h. m. 

39 

26 

53 



46.2 E. 

35.5 W. 

34.9 E. 

27.2 E. 

23.5 E. 
56.0 E. 

19.3 E. 

54.6 E. 
22 W. 



46.1 
0.0 
0.4 
26.4 
25.5 
21.5 
13.1"' 
19 54.7 
JO 4S.4 
5 32.6 



A COMET SEEKER. 



5.0 W. 



101. A Comet Seeker is a re- 
fracting telescope, with a large 
aperture and short focal distance. 
As comets cannot be found by 
their right ascension and declina- 
tion, but often have to be 
searched up, by sweeping around 
the heavens with a telescope, be- 
fore they become visible to the 
naked eye, it is important to 
have telescopes that will cover 
considerable space — that is, of 

wide aperture and short focal distance. Such a telescope was 
made by Mr. Fitz for Miss MitcheJ, of Newport, R. I 




REFLECTING TELESCOPES. 

102. The Reflecting Telescope is one in which the light is con- 
verged to a focus by means of 'a concave metallic reflector or 
speculum. Like the Refractors, they may be constructed with 
very little mounting ; though for convenience in use, it is neces- 
sary to place the reflector in. a tube. 



701. What is a comet 
scope. Simplest form ? 



Why necessary? 702. Describe a reflecting tele- 



322 



ASTRONOMY. 



SIMPLEST FORM OF A REFLECTING TELESCOPE. 




In this cut, the light A is seen passing from the object on the right, and falling upon 
the concave surface of the reflector at B, from which it is reflected back to a focus, and 
enters the eye of the observer at C. This telescope has no eye-piece. 

^03. The focal distance of a concave reflector is equal to half 
the radius of the sphere formed by the concave surface pro- 
duced. Hence to grind a reflector for a focus of 20 feet, it will 
be necessary to have the curve that of a circle whose radius is 
40 feet. 

FOCAL DISTANCE OF A CONCAVE REFLECTOR. 



B 














W ~~~"~~ 














B — ■ — ___ ___ 






-— CT~--^ 














^-^^^^ 






A 










^^^»fe£^ — 






















B — ^Z— — ^^-c^-""" 


B ___ — 3^_ — -^-- — 


¥n — ^-^^ — "~ 


W^^^~~ 



Here the curve of the speculum B is that of a circle, whose center 
is C ; while the focus of the speculum is at D, which is only bait 
the distance from B to C. 



T04. Reflecting telescopes are of several kinds — viz., the Gre- 
gorian, the Newtonian, the Cassegranian, the Herschelian, Sic. 
The Gregorian Reflector has an aperture in the center of the 
speculum, and a small concave mirror in the focus of the specu- 
lum, which reflects the light back through the aperture to the 
eye-piece. In this way the observer is enabled to face the 
object, and to direct the telescope toward it, as if it were a 
refractor. 



703. Focal distance ? 704. How many kinds of reflectors ? Describe the Gregorian. 
Why called Gregorian ? 



DIFFERENT KINDS OF TELESCOPES. 



323 



GREGORIAN REFLECTOR. 




Here the light A falls upon the speculum at B, and is reflected back to the small mir- 
ror C, by which it is thrown out through the aperture in the speculum, to the eye of the 
observer at D. The object is supposed to be off on the right, in the direction towards 
which the instrument is pointed. It is called a Gregorian telescope, after Mr. James 
Gregory, who first suggested the construction of reflecting telescopes. 

T05. The Newtonian Reflector is so called after Sir Isaac 
Newton, its inventor. Instead of a concave mirror in the focus 
of the speculum, he placed a plane mirror there, inclined so as 
to reflect the light to the side of the tube, where it was received 
by the observer. 

NEWTONIAN REFLECTOR. 




The light from the speculum is here shown falling upon the inclined mirror in the cen- 
ter, and reflected out to the eye of the observer. 

106. The Cassegranian Reflector is so called from M. Casse- 
grain, its inventor. It resembles the Gregorian, except that the 
speculum placed in the focus of the reflector is convex instead of 
concave. 

The Herschelian Reflector differs from all others, in having no 
small reflector whatever ; the light being reflected back to a 
focus at the top of the telescope, and near the edge of the tube, 
where the eye-piece is placed, and where the observer sits look- 
ing into the mirror with his back to the object. 

HERSCHELIAN TELESCOPE. 




Here the concave speculum is seen to be inclined a little to the lower side of the tube, 
go that the parallel rays A are reflected back to the observer at B, at the side of the 
instrument, where the eye-piece is placed. 



705. Newtonian reflectors ? 706. Cassegranian i 
eye-piece? How observer sit? 

14* 



Difference ? Herschelian ? Where 



324 



ASTRONOMY. 



TOT. The first telescope constructed upon this plan was that 
by Sir William Herschel, in 1*182. This was called his 20 feet 
reflector, and was the instrument with which he made many of 
his observations upon the double stars. In 1189, he completed 
his forty feet reflector, until recently the largest telescope ever 
constructed. 



WILLIAM HERSCHEL'S FORTY FEET REFLECTOR. 




108. The speculum of this instrument is 4 feet in diameter, 8^ 
inches thick, and weighed, before being ground, 2,118 pounds. 



707. First Herschelian telescope ? What called? Next? 708. Herschel's forty feet 
reflector? Size of Speculum? Weight? Tube? Length and weight ? How mounted? 



DIFFERENT KINDS OF TELESCOPES. 



325 



The tube is made of sheet iron riveted together, and painted 
within and without. 

The length of the tube is 39 feet 4 inches, and its weight 8,260 pounds. It is elevated 
or lowered by tackles, attached to strong frame-work ; and the observer, who sits in a 
chair at the upper end of the tube, and looks down into the reflector at the bottom, is 
raised and lowered with the instrument. Three persons are necessary to use this tele- 
scope — one to observe, another to work the tube, and a third to note down the observa- 
tions. A speaking tube runs from the observer to the house where the assistants are at 
work. By this telescope, the sixth and seventh satellites of Saturn were discovered ; 
and it was the chief instrument used by its distinguished owner, in making the observa- 
tions and discoveries which have immortalized his name, and which have so abundantly 
enriched and advanced the science of astronomy. 

LORD ROSSE'S GREAT REFLECTING TELESCOPE. 




T09. This is the largest reflecting telescope ever constructed. 
The speculum, composed of copper and tin, weighed three tons as 
it came from the mould, and lost about -Jth of an inch in grinding. 
It is 5^ inches thick, and 6 feet in diameter. It was cast on 
the 13th of April, 1842, and was cooled gradually in an oven for 
16 weeks, to prevent its cracking, by a sudden or unequal reduc- 
tion of the temperature. This speculum has a reflecting surface 
of 40*71 square inches. The tube is made of deal wood, one 
inch thick, and hooped with iron. Its diameter is seven feet, 
and its length 56. 

The entire weight of this telescope is twelve tons. It is mounted between two north 
and south walls, 24 feet apart, 72 feet long, and 48 feet high. The lower end rests upon 
an universal hinge. It can be lowered to the horizon, and raised to the zenith, and 
lowered northward till it takes in the Pole Star. Its motion from east to west is limited 

Observer where ? Usefulness? 709. Lord Rosse's telescope? Weight of speculum? 
Diameter? Thickness? Cooling? Tube? Entire weight? How mounted? What 



326 



ASTRONOMY. 



to 15 degrees. This magnificent instrument is situated at Burr Castle, Ireland. It was 
constructed by the Earl of Rosse, at an expense of $60,000. 

Speaking of this telescope, a late writer says : "By the energy and ingenuity of that 
eminent person (Lord Rosse), an eye is directed to the heavens, having a pupil six feet 
in diameter, with the most complete optical structure, and '-he power of ranging about 
for its objects over a great extent of sky; and thus the quantity of light which the eye 
secures from any point of the heavens is augmented, it may he, fifty thousand times. 
The rising Moon is seen from the Observatory in Ireland with the same increase of size 
and light, as if her solid globe, two thousand miles in diameter, retaining all its illumina- 
tion, really rested upon the summit of the Alps, to be gazed at by the naked eye. An 
object which appears to the naked eye a single star may, by this telescope, so far as its 
power of seeing is concerned, be resolved into fifty thousand stars, each of the same 
brightness as the obvious star.* 

110. A Transit Instrument is a telescope used for observing 
the transit of celestial objects across the meridian, for the pur- 
pose of determining differences of right ascension, or obtaining 
correct time. They are usually from six to ten feet long, and 
are mounted upon a horizontal axis, between two abutments of 
mason-work ; so that the instrument, when horizontal, will point 
exactly to the south. It will then take objects in the heavens, 
when they are exactly on the meridian. 



Let A D in the 
cut represent the 
telescope, and E 
and W the east 
and west abut- 
ments, between 
which it is 
placed. On the 
left is seen, at- 
tached to the ma- 
son work, a gra- 
duated circle ; 
and on the east- 
ern end of the 
axis of the tele- 
scope is seen an 
arm, n, extend- 
ing to the circle, 
as an index. 
Now, suppose the 
index n to be at 
o, in the upper 
part of the circle, 
when the tele- 
scope is horizon- 
tal; then if the 
meridian alti- 
tude of the object 
to be taken is 
10°, the index 
must be moved 
10° from o, as the 
degrees on the 
circle and the altitude of the object will correspond. 



A TRANSIT INSTRUMENT. 




Plurality of Worlds, American edition, p. 137. 



motion? Where located? Cost? Description by a late writer? Remarks upon its 
powers? 710. What is a transit instrument ? Size? How mounted? Describe parts 
as shown in the cut. How set the instrument for the meridian altitude of a star ? 



DIFFERENT KINDS OF TELESCOPES. 



327 



111. An Astronomical Clock is a clock adapted to keep exact 
sidereal time. Taking the vernal equinox in the heavens as the 
zero point, and reckoning 24 hours eastward to the same point 
again, the time — reckoning 15° to an hour — when an object 
crosses the meridian, will always represent the right ascension 
of the object. Hence right ascension is usually given in hours, 
minutes, and seconds ; or in time by the astronomical clock, set 
by the vernal equinox. 

712. A Mural Circle THE MCRAL circle. 

is a large graduated cir- 
cle, with a telescope 
crossing its center, used 
for the measurement of 
the altitudes and zenith 
distances of the heaven- 
ly bodies, at the instant 
of their crossing the 
meridian. They are 
usually fixed upon a 
horizontal axis, that 
turns in a socket firmly 
fixed in a north and 
south wall. The de- 
grees, minutes, and se- 
conds on the circle are 

read by means of microscopes, and indicate the altitude of the 
object. * 

Li the cut, A is a reading microscope firmly attached to the wall, and BCDE the 
wall to which the circle is attached. The telescope would denote an altitude of about 
40°, which would leave 5u° as the zenith distance. 




711. An astronomical clock? How set? How indicate right ascension of objects 9 
712. Describe a mural circle ? Its uses ? How mounted ? How ascertain altitude and 
zenith distances by it? 



328 



ASTRONOMY. 



CHAPTER XX. 

PEOBLEMS AND TABLES. 



PROBLEM I. 



TO CONVERT DEGREES, ETC., INTO TIME. 



Rule I. — Divide the degrees by 15, for hours ; and multiply 
the remainder, if any, by 4, for minutes. 

2. Divide the odd minutes and seconds in the same manner by 
15 for minutes, seconds, &c, and multiply each remainder by 4, 
for the next lower denomination. 



Example 1.- 
Thus, 



-Convert 32° 34' 45" into time. 
32°^15=2h. 8' 
34 -r-15 = 2 16" 

45-M5 = 3 



Ans. 32°34'45":=2h. 10' 19" 

Example 2. — If it is 12 o'clock at this place, what is the time 
20° east of us? 

Thus, fifteen in 20°, once, and five over ; the once is 1 hour f 
and the 5 multiplied by 4, gives 20 minutes ; the time is then 1 
hour and 20 minutes past 12. 

Example 3.— The longitude of Hartford is 12° 50' west of 
Greenwich ; what time is it at Greenwich when it is 12 o'clock 
at Hartford ? Ans. 4h. 51 min. 20 sec. 

Example 4. — When it is 12 o'clock at Greenwich, what is the 
time at Hartford ? Ans. 7h. 8m. 40s. 

Note. — Table VIII. is designed to facilitate calculations of this kind. The degrees 
being placed in one column, and the corresponding time in another, it needs no explana- 
tion, except to observe that degrees in the left-hand columns may be considered as so 
many minutes, instead of degrees ; in which case, the corresponding time in the adjoin- 
ing column, must be read as minutes and seconds, instead of hours and minutes. In 
like manner, the degrees in the left-hand column may be read as seconds, and the cor- 
responding time, as seconds and thirds. 

Example. — Find, by the table, the time correspoding to 32° 34' 45". 
Thus Against 32° is 2h. 8m, 

" 34' " 2 16s. 



8h. 10m. 



PROBLEMS AND TABLES 329 



PROBLEM II. 



TO CONVERT TIME INTO DEGREES, ETC. 

Rule. — Multiply the hours by 15, and to the product add one- 
fourth of the minutes, seconds, &c, observing that every minute 
of time makes £°, and every second of time J'. 

Example 1. — In 2 hours, 10 minutes, and 19 seconds ; how- 
many degrees ? 

Thus : 2h. 10m. 19s. 

15 

30° 
Add 10 quarters, or £ of the min. 2 30' 
Add 1 9 quarters, or \ of the sec. 4 45" 

Ans. 32° 34' 45" 

This problem is readily solved by means of Table IX., without the labor of calculation. 
Thus : . 2 hours =30° 

10 minutes = 2 30' 
19 seconds^ 4 45* 



Ans. 32° 34' 45" 

Ex. 2. — When it is 12 o'clock at Hartford, it is 4 hours, 51 
minutes, and 20 seconds past noon at Greenwich ; how many 
degrees is Hartford west of Greenwich ? 

Thus : 15 times 4 is 60— added to \ of 51, is 12° 45", and 
this increased by \ of 20, is 12° 50'. Ans. 

Ex. 3. — A Liverpool packet, after sailing several days from 
New York, finds the time by the Sun 2 hours and 40 minutes 
later than by the ship's chronometer : how far has the ship pro- 
gressed on her way ? 

Ex. 4. — A vessel leaves Boston, and having been tossed about 
in foul weather for some days, finds, that when it is 12 o'clock 
by the Sun, it is only 11 o'clock and 50 minutes by the watch ; 
is the vessel east or west of Boston • and how many degrees ? 

Ex. 5. — The moment of greatest darkness, during the annular 
eclipse of 1831, took place at New Haven, 10 minutes after 1 
o'clock. A gentleman reports that it happened precisely at 1, 
where he observed it ; and another, that it was 5 minutes after 
1 where he saw it : Quere. How far east or west were these 
gentlemen from each other, and how many degrees from New 
Haven ? 



330 ASTRONOMY. 



PROBLEM III. 



TO FIND WHAT STARS ARE ON THE MERIDIAN AT NINE O'CLOCK IN THE 
EVENING OF ANY GIVEN DAY. 

Rule. — Look for the given day of the month, at the bottom 
of the maps, and all the stars having the same degree of right 
ascension will be on the meridian at that time. 

Example 1. — What stars will be on the meridian at 9 o'clock, 
the 19th of January ? 

Solution. — On Map III. I find that the principal stars stand- 
ing over against the 19th of January, are Rigel and Capella. 

Ex. 2. — What stars are on the meridian the 20th of Decem- 
ber ? Ans. Menkar and Algol. 

PROBLEM IV. 
ANY STAR BEING GIVEN, TO FIND WHEN IT CULMINATES. 

Rule. — Find the star's right ascension in the table, or by the 
map (on the equinoctial), and the day of the month at the top 
or bottom of the map will be the day on which it culminates at 
9 o'clock. 

Example 1. — At what time is the bright star Sirius on the 
meridian ? 

Solution. — I find by the table, and by the map, that the right 
ascension of Sirius is 6 hours and about 38 minutes ; and the 
time corresponding to this, at the bottom of the map, is the 11th 
of February. 

Ex. 2. — At what time is Alpheratz, in the head of Andromeda, 
on the meridian ? Ans. The 9th of November. 

PROBLEM V. 

THE RIGHT ASCENSION AND DECLINATION OF A PLANET BEING GIVEN, 
TO FIND ITS PLACE ON THE MAP. 

Rule. — Find the right ascension and declination of the planet 
on the map, and that will be its place for the given day. 

Example 1. — Venus's right ascension on the 1st of January, 
1833, was 21 hours, 30 minutes, and her declination 16j° south ; 
required her situation on the map ? 

Solution. — On the right hand of the Plate II. I count off 



PROBLEMS AND TABLES. 331 

16f° from the equinoctial, on the marginal scale south, and from 
that point, 30 minutes to the left, or just half the distance 
between the XXI. and XXII. meridian of right ascension, and 
find that Yenus, that day, is within two degrees of Delta Capri- 
corni. near the constellation Aquarius, in the zodiac. 

Note. — It is to be remembered, that the planets will always be found within the limits 
of the zodiac, as represented in the maps. By means of Table VII., the pupil can find at 
any time the situations of all the visible planets, on the maps ; and this will enable him 
to determine their position in the heavens, without a chance of mistake. By this means, 
too, he can draw for himself the path of the planets from month to month, and trace 
their course among the stars. This is a pleasant and useful exercise, and is practised 
extensively in some academies. The pupil draws the map in the first place, or such a 
portion of it as to include the zodiacal constellations; then, having dotted the position 
of the planets from day to day, as indicated in Table VII., their path is easily traced with 
a pen or pencil. 

Ex. 2 — Mars' right ascension on the 13th of March, 1833, is 
5 hours, 1 minute, and his declination 24f° north ; required his 
situation on the map ? 

Solution. — I find the fifth hour line or meridian of right ascen- 
sion on Plate III., and counting upwards from the equinoctial 
24f °, I find that Mars is between the horns of Taurus, and 
about 5° S. W. of Beta Aurigae. 

Ex 3. — Required the position of Jupiter and Saturn on the 
13th of February and the 25 th of May ? 

When the right ascension and declination of the planets are not given, they are to be 
sought in Table VII. 

PROBLEM VI. 

TO FIND AT WHAT MOMENT ANY STAR WILL PASS THE MERIDIAN ON A 

GIVEN DAY. 

Rule. — Subtract the right ascension of the Sun from the 
star's right ascension, found in the tables : observing to add 24 
hours to the star's right ascension, if less than the Sun's, and 
the difference will show how many hours the star culminates 
after the Sun. 

Example 1. — At what time will Procyon pass the meridian on 
the 24th of February ? 

Solution. — R. A. of Procyon, 1h. 30m. 33s. + 24h. 

31 30' 33' 
R A. of Sun, 24th Feb. 22 29 1 



Ans. 9 1 32 

That is, lm. 32s. past 9 o'clock in the evening. 

Ex. 2. — At what time will Denebola pass the meridian on the 
first of April ? 



332 ASTRONOMY. 

Solution.— R. A. of Denebola is llh. 40' 32" 

R. A. of Sun, April 1, 41 25 



Ans. 10 59 1 

That is, at 59 minutes, *l seconds, past 10 in the evening. 

Ex. 3. — At what time on the first day of each month, from 
January to July, will Alcyone, or the Pleiades, pass the meri- 
dian ? 

Ex. 4. — At what time will the Dog-Star, or Sirius, culminate 
on the first day of January, February, and March ? 

Ex. 5. — How much earlier will Spica Yirginis pass the meri- 
dian on the 4th of July, than on the 15th of May ? — Ans. 3 
hours, 25 minutes. 

PROBLEM VII. 

TO FIND WHAT STARS WILL BE ON OR NEAREST THE MERIDIAN AT ANY 
GIVEN TIME. 

Rule. — Add the given hour to the Sun's right ascension, 
found in Table III., and the sum will be the right ascension of 
the meridian, or mid-heaven ; and then find in Table II. what 
star's right ascension corresponds with, or comes nearest to it, 
and that will be the star required. 

Example 1. — What star will be nearest the meridian at 9 
o'clock in the evening of the 1st September ? 
Solution. — Sun's right ascension 1st September, 

lOh. 40' 30" 
Add the time from noon 9 



Right ascension of the meridian 19h. 40' 30" 

Now all the stars in the heavens which have this right ascen- 
sion, will be on the meridian at that time. On looking into 
Table II. the right ascension of Altair, in the Eagle, will be 
found to be 19h. 40m. ; consequently Altair is on the meridian 
&': the time proposed ; and Delta, in the Swan, is less than two 
minutes past the meridian. 

Ex. 2. — Walking out in a bright evening on the 4th of Sep- 
tember, I saw a very brilliant star almost directly overhead ; I 
looked on my watch, and it wanted 20 minutes of 8 ; required 
the name of the star ? 



PROBLEMS AND TABLES. 333 

Solution. — Sun's declination 4th of September, 

lOh. 51' 22" 

Add the time from noon 1 40 



Gives R. A. of Lyra, nearly 18 31 22 

Ex. 3. — About 8-J- minutes after 8 in the evening of the 11th 
of February, I observed a bright star on the meridian, a little 
north of the equinoctial, and 1 minute before 9 a still brighter 
one, further south ; required the names of the stars ? 

PROBLEM VIII. 

TO FIND WHAT STARS WILL CULMINATE AT NINE O'CLOCK IN THE EVEN- 
ING OF ANY DAY IN THE YEAR. 

Rule. — Against the day of the month in Table IV., find the 
right ascension of the mid-heaven, and all those stars in Table 
II. which have the same, or nearly the same right ascension, will 
culminate at 9 p.m. of the given day. 

Example 1. — What star will culminate at 9 in the evening of 
the 26th of March ? 

Solution. — I find the right ascension of the meridian, at 9 
o'clock in the evening of the 26th of March, is 9h. 19' 31"; and 
on looking into Table II., I find the right ascension of Alphard, 
in the heart of Hydra, is 9h. 19' 23". The star is Alphard. 

Ex. 2. — What star will culminate at 9 in the evening of the 
28th of June ? Ans. Aphacca. 

PROBLEM IX. 

TO FIND THE SUN's LONGITUDE OR PLACE IN THE ECLIPTIC, ON ANY 
GIVEN DAY. 

Rule. — On the lower scale, at the bottom of the Planisphere 
(Map VIII.) look for the given day of the month ; then the 
sign and degree corresponding to it on the scale immediately 
above it will show the Sun's place in the ecliptic. 

Example 1. — Required the Sun's longitude, or place in the 
ecliptic, the 16th of September. 

Solution. — Over the given day of the month, September 16th, 
stands 5 signs and 23 degrees, nearly, which is the Sun's place 
in the ecliptic at noon on that day ; that is, the Sun is about 23 
degrees in the sign Virgo. 



334 ASTRONOMY. 

N.B. — If the 5 signs be multiplied by 30, and the 23 degrees be added to it, it will give 
the longitude in degrees, 173. 

Ex. 2. — Required the Sun's place in the ecliptic at noon, on 
the 10th of March. 

PROBLEM X. 

GIVEN THE SUN'S LONGITUDE, OR PLACE IN THE ECLIPTIC, TO FIND HIS 
RIGHT ASCENSION AND DECLINATION. 

Rule. — Find the Sun's place in the ecliptic (the curved lice 
which runs through the body of the planisphere), and with a 
pair of compasses take the nearest distance between it and the 
nearest meridian, or hour circle, which being applied to the gra- 
duated scales at the top or bottom of the planisphere (measur- 
ing from the same hour circle), will show the Sun's right ascen- 
sion. Then take the shortest distance between the Sun's place 
in the ecliptic and the nearest part of the equinoctial, and apply 
it to either the east or west marginal scales, and it will give the 
Sun's declination. 

Example 1. — The Sun's longitude, September 16th, 1833, is 
5 signs, 23 degrees, nearly ; required his right ascension, and 
declination. 

Solution. — The distance between the Sun's place in the eclip- 
tic and the nearest hour circle being taken in the compasses, and 
applied to either the top or bottom graduated scales, shows the 
right ascension to be about 11 hours 35 minutes ; and the dis- 
tance between the Sun's place in the ecliptic, and the nearest 
part of the equinoctial, being applied to either the east or west 
marginal scales, shows the declination to be about 2° 45', which 
is to be called north, because the Sun is to the northward of 
the equinoctial ; hence the Sun's right ascension, on the given 
day, at noun, is about 11 hours 35 minutes, and his declination 
2° 45' N. 

Ex. 2.— The Sun's longitude, March 10th, 1833, is 11 signs, 
19 degrees, nearly ; required his right ascension and declina- 
tion ? 

Ans. R. A. 23h. 21m. Decl. 4° 11' nearly. 

problem XI. 

TO FIND THE RIGHT ASCENSION OF THE MERIDIAN AT ANY GIVEN TIME. 

Rule. — Find the Sun's place in the ecliptic by Problem IX., 
and his right ascension by Problem X., to the eastward of 



PROBLEMS AND TABLES. 335 

which count off the given time from noon, and it will show the 
right ascension of the meridian, or mid-heaven. 

Example 1. — Required the right ascension of the meridian 9 
hours, 25 minutes past noon, September 16th, 1833 ? 

Solution. — By Problems IX. and X., the Sun's right ascen- 
sion at noon of the given day, is 11 hours 35 minutes ; to the 
eastward of which, 9 hours and 25 minutes (the given time) 
being counted off, shows the right ascension of the meridian to 
be about 21 hours. 

Ex. 2. — Required the right ascension of the meridian at 6 
hours past noon, March 10th, 1833 ? 

Solution. — By Problems IX. and X., the Sun's right ascension 
at noon of the given day, is 23 hours and 21 minutes ; to the 
eastward of which, the given time, 6 hours, being counted off, 
shows the right ascension of. the meridian to be about 5 hours, 
21 minutes. 

Remark. — In this example, it may be necessary to observe, that where the eastern, or 
left-hand extremity of the planisphere leaves off, the western, or right-hand extremity 
begins ; therefore, in counting off the given time on the top or bottom graduated scales, 
the reckoning is to be transferred from the left, and completed on the right, as if the two 
outside edges of the planisphere were joined together. 

PROBLEM XII. 

TO FIND WHAT STARS WILL BE ON OR NEAR THE MERIDIAN, AT ANY 
GIVEN TIME. 

Rule. — Find the right ascension of the meridian by Problem 
XI., over which lay a ruler, and draw a pencil line along its 
edge from the top to the bottom of the planisphere, and it will 
show all the stars that are on or near the meridian. 

Example 1. — Required what stars will be on or near the 
meridian at 9 hours, 25 minutes past noon, Sept. 16th, 1833 ? 

Solution. — The right ascension of the meridian by Problem 
XI. is 21 hours : this hour circle, or the line which passes up 
and down through the planisphere, shows that no star will be 
directly on the meridian at the given time ; but that Alderamin 
will be a little to the east, and Deneb Cygni a little to the west 
of it ; also Zeta Cygni, and Gamma and Alpha in the Little 
Horse, very near it on the east. 

PROBLEM XIII. 
TO FIND THE EARTH'S MEAN DISTANCE FROM THE SUN. 

Rule. — As the Sun's horizontal parallax is to radius, so is 
the semi-diameter of the Earth to its distance from the Sun. 



336 ASTRONOMY. 

By Logarithms. — As tangent of the Sun's horizontal parallax 
is to radius, so is the Earth's semi-diameter to her mean distance 
from the Sun. 

8".5776 : 206264\8 : :3962 : 95,273,869 miles. 
By Logarithms. 
As tangent of the Sun's horizontal parallax, 8".5776= 5.6189407 
Is to radius, or 90°, =10-0000000 

So is the Earth's semi-diameter, 3962= 3.5979143 

To the Earth's distance, 95,273,869= 7.9789738 

PROBLEM XIV. 

TO FIND THE DISTANCE OF ANY PLANET FROM THE SUN, THAT OF THE 

EARTH BEING KNOWN. 

Rule. — Divide the square of the planet's sidereal revolution 
round the Sun, by the square of the Earth's sidereal revolution, 
and multiply the cube root of the quotient by the Earth's mean 
distance from the Sun. 

By Logarithms. — From twice the logarithm of the planet's 
sidereal revolution, subtract twice the logarithm of the Earth's 
sidereal revolution, and to one-third of the remainder, add the 
logarithm of the Earth's mean distance from the Sun. 

Example. — Required Mercury's mean distance from the Sun, that of the Earth being 
95,273,869 miles. 

Mercury's sidereal revolution is 87.969258 days, or 7600543". 8912 : the Earth's sidereal 
revolution is 365.256374417 days, or 

31 558151 ".5 7600543.9 

31558151". 5 7600543.9 



995916962096952.25 by which divide 57768267575827.21 
and the quotient will be 0.052005106713292, the cube root of which is 0.3870977, and this 
multiplied by 94,881,891, gives 36,727,607 miles, for Mercury's distance from the Sun. 
This problem may be performed by logarithms in as many minutes as the former method 
requires hours. 

Mercury's Sid. Rev. 7600543".9 log. =6.8808447 x 2 13.7616S94 

Earth's Sid. Rev. 31558151". log.=7.4991302 x2 14.9982604 



y 3 )— 2.7634290 



1.587S097 
Add log. of the Earth's mean distance, 7.97S9738 



Mercury's distance, 36,880,422. Ans. 7.5667835 

If the pupil have not already learned the use of logarithms, this problem will satisfy 
him of their unspeakable advantage over all other modes of computation. By reviewing 
the above calculation, he will perceive that instead of multyplying 31558151'.5 by itself, 
he need only multiply its logarithms by two ! and instead of extracting the cube root of 
0.058005106713292, he need only divide its logarithm by three ! and instead of multiply- 
ing 0.3870977, by 95,273,869, he need only add their logarithms together. He need not 
think himself a dull scholar, if by the former method he come to the true result in Jive 
hours ; nor remarkably quick, if by the latter he come to it in Jive minutes. 

PROBLEM XV. 

TO FIND THE HOURLY MOTION OF A PLANET IN ITS ORBIT. 

Rule. — Multiply the planet's mean distance from the Sun by 



PROBLEMS AND TABLES. 337 

6.2831853, and divide the product by the time of the planet's 
sidereal revolution, expressed in hours, and the decimals of an 
hour. 

By Logarithms. — Add 0.T981199 to the logarithm of the 
planet's mean distance from the Sun, and from the sum subtract 
the logarithm of the planet's revolution expressed in hours. 

Example. — Required the Earth's hourly motion in its orbit. 

Log. of Earth's distance=7.9780738 + 0.7981799= 8.7771537 

Subtract log. of Earth's revolution 3.9428090 

Gives Earth's horary motion, 68,288 miles, 4.834344T 

PROBLEM XVI. 
TO FIND THE HOURLY MOTION OF A PLANET ON ITS AXIS. 

Rule. — Multiply the diameter of the given planet by 3.14159, 
and divide the product by the period of its diurnal rotation. 

By Logarithms.— -AM 4.0534524 to the logarithm of the 
planet's diameter, and from the sum subtract the logarithm of 
its diurnal rotation, expressed in seconds. 

Earth's diameter, 7924 log. = 3.8989445 

Add log. of 3600" + log. of 3.14159 = 4.0534524 



7.! 
Subtract log. diurnal rotation, 23h. 56' 4".09 = 4.9353263 



Ans. 1040.09 miles = 3.0170706 

i 
PROBLEM XVII. 

TO FIND THE RELATIVE MAGNITUDE OF THE PLANETS. 

Rule. — Divide the cube of the diameter of the larger planet 
by the cube of the diameter of the less. 

By Logarithms. — From three times the logarithm of the 
larger, subtract three times the logarithm of the less. 

Example. — How much does the size of the Earth exceed that of the Moon ? 
Earth's diameter, 7912 log. 3.S9S2863 x 3= 11.6948589 

Moon's diameter, 2160 log. 3.3343376 x 3= 10.0030128 

The Earth exceeds the Moon, 49.1865 times. Ans. 1.6918461 

In this example, 7912 miles is assumed as the mean between the Earth's equatorial 
and polar diameter : the former being 7924, and the latter 7898 miles. 

PROBLEM XVIII. 

TO FIND THE PROPORTION OF SOLAR LIGHT AND HEAT AT EACH OF 
THE PLANETS. 

Rule. — Divide the square of the planet's greater distance 
from the Sun, by the square of the less. — Or, subtract twice the 
logarithm of the greater distance from twice the logarithm of 
the less. 



338 



ASTRONOMY. 



Example. — How much greater is the Sun's light and heat at 
Mercury, than at the Earth ? 



Log. of Earth's distance 

" of Mercury's 
Ans. 6.6736 times greater= 



T.9789738 x 2=15.9579476 

7.5667959 x 2=15.1335918 

0.8243558 



PROBLEM XIX. 
TO FIND THE CIRCUMFERENCE OF THE PLANETS. 

Rule. — Multiply the diameter of the planet by 3.14159; or, 
add the logarithm of the planet's diameter to 0.49 7 1499. 

PROBLEM XX. 
TO FIND THE CIRCUMFERENCE OF THE PLANETARY ORBITS. 

Rule. — Multiply the planet's mean distance from the Sun by 
6.2831853 ; or, to the logarithm of the planet's mean distance, 
add 0.1981799, and the sum will be the logarithm of the answer. 

PROBLEM XXI. 

TO FIND IN WHAT TIME ANY OF THE PLANETS WOULD FALL TO THE 
SUN, IF LEFT TO THE FORCE OF GRAVITATION ALONE. 

Rule. — Multiply the time of the planet's sidereal revolution 
by 0.176776 ; the result will be the answer. 

By Logarithms. — From the logarithm of the planet's sidereal 
revolution, subtract 0.7525750, and the remainder will be the 
logarithm of the answer, in the same denomination as the side- 
real revolution. 

Required the times, respectively, in which the several planets would fall to the Sun by 
the force of gravity. 



Planets would fall to the Sun. 


Days. 


H. 


M. 


S. 


Logarithms. 




Mercury, 


15 


13 


13 


16 


6.1282686 




Venus, 


39 


17 


19 


22 


6.5355424 




Earth, 


64 


13 


38 


55 


6.7465357 




Mars, 


121 


10 


36 


3 


7.0208817 




Jupiter, 


265 


21 


33 


35 


7.8206849 




Saturn, 


1901 


23 


24 


4 


8.2157186 




Herschel, 


5424 


16 


52 


1 


8.6708897 




Moon to the Earth, 


4 


19 


54 


57 


5.6204459 





THE END. 



EXPLANATIONS A1STD PEOBLEMS 



ADAPTED TO 



WHITALL'S PLANISPHERE. 



Note. — This is a movable Planisphere, invented and copy- 
righted by Henry Whitall, and for sale by the publishers of Bur- 
ritt's Geography of the Heavens, exhibiting the stars that are rising, 
setting, on the meridian, or their position in the firmament, as 
seen in the United States every five minutes for hundreds of 
years. The right ascension and declination of the sun, moon, 
stars, and planets ; the equation of time (sun fast or slow) ; har- 
vest moon ; sun and moon running high and low ; the milky way, 
as it changes its course for every hour ; change of seasons, etc., 
can be readily explained with this invaluable substitute for a Ce- 
lestial Globe, " being as much better as it is cheaper" than that 
expensive school apparatus. 

It is light, portable, accurate, containing much within a small 
space, and is sold at the moderate price of two dollars, which 
brings it within the means of all lovers of science, and of every 
teacher who may desire his pupils to become acquainted with the 
wonders of the heavens. This knowledge need no longer be con- 
fined to the learned few, for the use of this Planisphere will enable 
any one to become familiar with the stars and constellations, and 
will prove both pleasing and instructive. The desideratum so 
long desired is thus supplied, and reading the stars is no longer a 
mystery. 



340 EXPLANATIONS AND PROBLEMS 

PROBLEMS 

WHICH MAT BE PERFORMED ON THE PLANISPHERE. 

THE DAY OF THE MONTH, THE HOUR AND MINUTE BEING GIVEN, 
TO FIND WHAT STARS ARE RISING, SETTING, ON THE MERIDIAN, 
OR IN ANY PART OF THE FIRMAMENT. 

Application. — Bring the given day of the month to 12 noon, 
turn the index to the given hour and minute, hold it overhead, 
with the meridian line, north and south; the Planisphere will 
then represent in miniature the constellations visible in the heav- 
ens at that time. The stars which are rising are near the eastern, 
and those setting near the western horizon. And thus can be seen 
the stars in any part of the heavens, at all times, sufficiently accu- 
rate for most practical purposes. 

Example. — Given this evening at 9 o'clock, or any other time, to find what 
stars are rising in the east, setting in the west, those in the northern or south- 
ern horizon, in the zenith, or in any other part of the firmament. 

Example. — "Where will An-drom'e-da be on the 10th of November at 10 
o'clock ? (29.) Ans. Directly over head. 

Example. — Where will the Pleiades be 10 minutes before 9 o'clock on the 
evening of the 1st of January? (66.) Ans. On the meridian. 

Example. — "What remarkable cluster of stars rise between the N.E. and 
N.E. by E. points of the horizon, at half past 8 o'clock, P. M., on the 6th of 
September ? Ans. Ple'ia-des, or seven stars. 

Example. — "What bright star will set near the N."W. by W. about 5 min- 
utes before 11 o'clock on the 6th of September ? Ans. Arc-tu'rus. 

Example. — What star will rise in the E.S.E. at 8 o'clock on the 20th of 
December ? And what star will set about 15 minutes later in the W. by N. ? 
Ans. Sir'i-us, the brightest fixed star, and Altair. 

Example. — What stars will be on and near the meridian about 8 o'clock 
on the 21st of November? Ans. Caph. in Cas-si-o-pe'ia, Alpherafcz in An- 
drom'e-da, and Algon-ib in PegVsus, marking out the first meridian. 

TELESCOPIC OBJECTS. 

The right ascension of the telescopic objects are given in hours 
and minutes. To find their place in the heavens, bring the 21st 
of March to 12 noon; turn the index to the hour and minute of 
E. A. ; opposite the declination, marked on the meridian, will be 
the situation of the object; on the equator opposite can be seen 
the degrees of R. A. 



ADAPTED TO WHITALL'S PLANISPHERE. 341 

Should the E. A. be 13 hours, bring the index to 1, past mid- 
night; for 14 hours bring it to 2. 

a Yirginis (Spica) E. A. 13 hours, 16 minutes, 47 seconds, turn 
the index to 1 hour, 16 minutes past midnight, and its place is 
10° 19' 5" south of the equator. 

a Bo-o'tis (Arcturus) E. A. 14 hours, 8 minutes, 23 seconds, turn 
the index to 2 hours, 8 minutes, 22 seconds past midnight, its 
place will be under the 20° mark on the meridian, north of the 
equator. 

a Scorpii (Antares) E. A. 16 hours, 19 minutes, 36 seconds, turn 
the index to 4 hours, 19 minutes, 36 seconds past midnight, and 
its place is 26° 04' 3" south its declination. 

THE RIGHT ASCENSION AND DECLINATION OF THE SUN, MOON, 
PLANET, STAR, Or COMET, BEING GIVEN, TO FIND ITS PLACE ON 
THE PLANISPHERE. 

Bring the graduated side of the meridian to the degrees of right 
ascension marked on the equator. 

Its place will be under the declination marked on the meridian. 

Example. — Given the right ascension of a star 212°, declination 20° north. 
To find its place on the Planisphere. (169.) Ans. Arc-tu'ras. 

Example.— What star has its E. A. 342°, D. 30^° south? Ans. Ee'mal- 
haut. 

TO FIND THE RIGHT ASCENSION AND DECLINATION OF THE SUN FOR 
EVERY DAT OF THE TEAR. 

The sun's place among the stars, is on the ecliptic where the day 
of the month is. Bring the meridian to the day required. The 
decimation will be found opposite on the meridian, and the right 
ascension opposite 0, on the equator. 

Or, bring the day of the month to 12 noon, turn the index there 
also ; on the meridian meets the equator, where will be found 
the degrees of right ascension. The day of the month (the sun's 
place among the stars), will be where the meridian meets the 
ecliptic, and the declination opposite on the meridian. 

Example. — What is the right ascension and declination of the sun on the 
21st of March? Ans. 0. 

Example. — What is the right ascension and declination of the sun on the 
22d of June? Ans. 90° R. A., 23^° N". D. 

What is the right ascension and declination of the sun on the 2 2d of De- 
cember? Ans. 270° R. A., 23-p S. D. 



342 -EXPLANATIONS AND PROBLEMS 

TO FIND ON WHAT DAY OF THE YEAR ANY STAR PASSES THE MERI- 
DIAN AT A GIVEN HOUR OR MINUTE. 

Bring the meridian to the centre of the star, by the ribbons turn 
the Planisphere until the index meets the given time. Opposite 
12, noon, will be found the day required. 

Example. — When will Reg'-u-lus be on the meridian at 9 o'clock, evening ? 
(124.) Ans. 5th of April. When will Altair be on the meridian at 9^- o'clock, 
evening? Ans. 25th of August. 

When will Arcturus be on the meridian at 9 o'clock? (169.) Ans. 9th 
of June. 

When will a Spica Yirginis be on the meridian at 9 o'clock in the evening ? 
(162.) Ans. About the 28th of May. 

THE DAY OF THE MONTH BEING GIVEN, TO FIND AT WHAT TIME ANY 
STAR WILL COME TO THE MERIDIAN. 

Bring the day of the month to 12 noon. Turn the graduated 
side of the meridian to the centre of the star. The index will 
point out the time required. 

Example. — At what time will a Vega come to the meridian, on the 25th 
of August? Ans. 8 o'clook, 15 minutes. 

At what hour will An-ta'res, in Scorpio, come to the meridian on the 10th 
of July? (199.) Ans. 9 o'clock. 



TO CONVERT TIME INTO DEGREES, OR DEGREES INTO TIME. 

Bring the 21st of March to 12 noon. Turn the index to the 
same point. The movable meridian and first meridian coincide, 
from which the right ascension of all the heavenly bodies is mea- 
sured east on the equator, counting 10, 20 to 360 degrees, to the 
vernal equinox or place of beginning. 

The index will point to the hour and minute of right ascension 
reading 12, 13 to 24 hours. One degree on the equator being 
equal to 4 minutes pointed out by the index, fifteen degrees equal 
to one hour, so on the equator can be read degrees, and the index 
shows the hours and minutes of right ascension. 

Example. — 100° on equator equal 6 hours 40 minutes, shown by index. 
212° equal 14 hours, 8 minutes. 276£° equal 18 hours, 26 minutes. 

The sun fast or slow depends upon two causes, viz. : the obliq- 
uity of the ecliptic and the unequal motion of the earth in its 



ADAPTED TO WHITALL S PLANISPHERE. 343 

orbit. The Planisphere will indicate the equation of time depend- 
ent upon the former. Bring the graduated side of the meridian 
to 30° on the equator (mean clock time), note the time shown by 
the index. Then bring the meridian to 30° on the ecliptic (sun's 
or apparent time), the sun is as many minutes fast, as it is west of 
mean clock time shown by the index. Again, bring the meridian 
to 150° on the equator, the sun is then as many minutes slow as 
30° (the fifth sign on the ecliptic) is east of mean time shown by 
the index. (397.) 

The Seasons — different length of days and nights. — An illus- 
tration of (616), bring the 20th of March to 12 noon, turn the 
index to 6, morning, the 20th day of March (or sun's place on the 
ecliptic), will be near the eastern horizon; turn the index to 6, 
evening, the sun's place will be found setting near the west, thus 
showing the days and nights to be equal. 

Bring the 21st of June to 12 noon, find that day on the ecliptic, 
turn the index until the day found meets the north-eastern horizon, 
and the index will show about the time the sun rises ; turn the 
index until the north-western horizon meets the same day, when 
the index will show near the time of the sun setting, thus showing 
the days to be about four hours longer than they are on the 20th 
of March, and the nights that time shorter. 

(61*7.) Bring the 21st of December to 12 noon, find the day on 
the ecliptic, and turn the index until the south-eastern horizon 
meets the day, the index will point nearly to the time of the sun's 
rising; turn the index until the south-western horizon meets the 
same day for the approximate time of setting, thus showing the 
days to be about four hours shorter than they are on the 23d of 
September, and the nights that much longer. 

The Harvest Moon (626 — 635) (so called in some parts of Eu- 
rope) is of great benefit to the husbandman by lengthening the 
day while gathering the fruits of the earth, and takes place at the 
full moon in September, when the moon rises for several evenings 
near the same hour. Shown on the Planisphere by bringing the 
15th day of September to 12 noon, and turning the index to 6^ 
o'clock evening. The eastern horizon, first meridian, ecliptic, and 
equator, meet at the vernal equinox. Should the moon full on 
that day, and rise with the vernal equinox at 6£ o'clock ; on the 
following evening, she will have gained about 12° on the sun, then 
turn the index until 12° on the ecliptic rises, note the time showD 



344 EXPLANATIONS AND PROBLEMS 

by the index, bring 12° more up again, note the time. Thus it 
can be seen that when the ecliptic is nearest parallel to the hori- 
zon, the difference of time in the moon's rising is least, and setting 
greatest; when the ecliptic is nearest perpendicular to the horizon, 
then will be the greatest difference of time in her rising, and the 
least in setting. 

IN SUMMER, WHEN THE SUN RUNS HIGHEST, THE FULL MOON RUNS 
LOWEST. IN WINTER, WHEN THE SUN RUNS LOWEST, THE FULL 
MOON RUNS HIGHEST. (421.) 

Bring the 2 2d of June to 12 noon. Turn the index to the same 
point; where the meridian meets the ecliptic will be found the day 
of the month (sun's place among the stars), at his greatest distance 
north, shown by the degrees marked on the meridian. Should 
the moon full on that day, she will be found in the opposite part 
of the firmament, shown by bringing the index to 12 midnight, to 
be within 5° of where the meridian meets the ecliptic, at her 
greatest distance south. Turn the index to about 8 o'clock even- 
ing. The sun's place of setting will be shown near N.W. by W., 
and moon's place of rising near S.E. by E. 

Tn winter bring 2 2d of December to 12 noon, turn the index 
there also, where the meridian meets the ecliptic will be the sun's 
place at his greatest distance south. Should the moon full on that 
day, she will be in the opposite part of the heavens. Shown by 
bringing the index to 12 midnight, to be near the ecliptic at her 
greatest distance north. Turn the index to 4 o'clock afternoon, 
the sun will be found to set near S.W. by W., and full moon to 
rise near N.E. by E. 

GIVEN THE DAY AND HOUR, TO TELL THE COURSE AND POSITION OF 
THE MILKY WAY. 

Bring the day of the month to 12 noon, turn the index to the 
given time, the course and position can be readily traced on the 
Planisphere. (256—260.) 

Example. — What will be the course of the milky way on the 5th of Sep- 
tember at 6, 9, 12, and 5 o'clock? Ana. At 6 o'clock evening, starting from 
northern horizon, to east of zenith, to southern horizon. At 9 o'clock it ap- 
pears in the KE., in zenith, to S.W. At 12 midnight it appears in REE., 
passes meridian at 60° north, to the W.S.W. At 5 o'clock, morning, it ap- 
pears in the S.E., passes the zenith, to the N.W. 



ADAPTED TO WHITALL'S PLANISPHERE. 345 

GIVEN THE TIME OF THE MOON OR PLANET'S SOUTHING, TO FIND ITS 
PLACE AMONG THE STARS. 

Bring the day of the month, to 12 noon. Turn the index to the 
hour and minute, the moon or planet souths, or comes to the me- 
ridian, its place will be near where the graduated side of the me- 
ridian meets the ecliptic. 

To find when it will rise, turn the index until the eastern hori- 
zon meets the place found on the Planisphere; the index points 
out the time. Bring the western horizon there for the time of 
setting. 



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